10mm-Auto

Picked up the RMW Grease Gun lower today. That thing is built like a TANK! A nicely built tank.

Received the 11" 10mm upper last Saturday. It came with the lower hardware, 1 grease gun mag, stock, etc. Not a bad deal. I have a POF trigger. I have ordered Diamondhead polymer sights and an Ergo grip. Oh and a pistol tube for testing. That should be everything. Once it proofs out, then I file with the ATF.

Started assembling the lower. Stuck at the bolt release roll pin. I need a roll pin starter punch/holder. It will go but I don't want to wail on the thing.

All is good - will take pictures at some point.

Here are a couple in work shots of my newest project as mentioned above.

(http://pws.cablespeed.com/~pablomail//10mmAR1.JPG)

(http://pws.cablespeed.com/~pablomail//10mmAR2.JPG)

Whats the chamber support look like?

Quote from: Hermit on February 25 2015 02:23:51 AM MST
Whats the chamber support look like?

Good question! It's pretty darn nice, like perfect. Better than any 10mm semi-automatic handgun I've groped. (I've not seen a S&W 610, so fair warning there). I'm going to run some hot stuff in this one methinks.

My gun trust successfully efiled the SBR eform last night.

I was starting to think some of my posts here are invisible  :D Thanks for the response!

On Sunday I dialed in the mag catch:

(http://pws.cablespeed.com/~pablomail//10mmAR3.JPG)

(http://pws.cablespeed.com/~pablomail//10mmAR4.JPG)

(http://pws.cablespeed.com/~pablomail//10mmAR5.JPG)

I finished the bolt, bolt handle and installed the Diamond Head Polymer sights (lightweight but great sights)

http://www.diamondhead-usa.com/collections/polymer-sights/products/polymer-diamond-integrated-sighting-system-with-nitebrite

Upper is complete!

Still wanting for my roll pin starters to finish the lower!!

That said I got all the acknowledgement emails from ATF.

Quote from: Pablo on February 25 2015 04:45:45 AM MST

Quote from: Hermit on February 25 2015 02:23:51 AM MST
Whats the chamber support look like?

Good question! It's pretty darn nice, like perfect. Better than any 10mm semi-automatic handgun I've groped. (I've not seen a S&W 610, so fair warning there). I'm going to run some hot stuff in this one methinks.

My gun trust successfully efiled the SBR eform last night.

I was starting to think some of my posts here are invisible  :D Thanks for the response!

iv been pondering on picking one of these up since i dont own a ar or 223 but i have a few 10s...if i do get one id probably go the sig brace route if i still can at the time

Mine is still a pistol. So testing will occur with a Sig brace and a pistol buffer tube.

Here is the completely finished upper (well I still need to Loctite things):

(http://pws.cablespeed.com/~pablomail//FinishedUp.JPG)

The lower......I just finally got my roll pin starter for the bolt release lever roll pin. Wow that bad boy saved my bacon. Anyway got that done and installed the safety lever and cheezy kit grip. Waiting on pistol tube now. Slow!!! Lower almost done. No scratches or dings.

You are making me want one of these.  :P

The atf changed their rules on the sig brace http://www.grandviewoutdoors.com/articles/5327-atf-says-shouldering-sigtac-brace-illegal#sthash.ulti6WQl.dpbs

I am aware of that.  Not sure what your point is (?)

I really wanna see them argue in court that a you become a felon based on how you hold a gun.

The rest of the parts arrived today. I have another 10mm pistol now.

Did I mention this thing looks completely bad ass with the grease gun magazine hanging down? M3 meet AR. Yeah baby. Need to hit the range.

Quote from: sqlbullet on February 27 2015 02:20:10 PM MST
I really wanna see them argue in court that a you become a felon based on how you hold a gun.

While I agree I don't want to go up against the atf in court.

Quote from: 10mmfan on February 27 2015 03:21:05 PM MST

Quote from: sqlbullet on February 27 2015 02:20:10 PM MST
I really wanna see them argue in court that a you become a felon based on how you hold a gun.

While I agree I don't want to go up against the atf in court.

Eh they'll finally ban it after they get all the cheap surplus ammo dried up

Lousy Picture:

(http://pws.cablespeed.com/~pablomail//ARPistol1.JPG)

Close up of mags (one modified for 10mm and AR lower) and Underwood 200gr.

(http://pws.cablespeed.com/~pablomail//GGMags1.JPG)

Here is my modified UpLula:

(http://pws.cablespeed.com/~pablomail//mag1.JPG)
(http://pws.cablespeed.com/~pablomail//mag2.JPG)
(http://pws.cablespeed.com/~pablomail//mag3.JPG)

This thing is fighting with me. Does anyone here know the products and got a 10mm running right? It's missfeed city right now. I shipped the upper back to Ron with the magazine. So close, yet so far!

Let us know

I expect it will come back to running well

He is getting closer. The upper duplicated the issue in his lower when he went over 5 rounds. He thinks it's a  follower issue in his supplied mag. I  suggested he start with a virgin magazine and convert it.

Any updates?

Sorry I was negligent in responding. Bottom line is the mag follower was subtly wrong. The problem shows up more frequently the more rounds in the magazine 15-20 or more (Ron only shoots 5). Ron fixed the magazine and modified a virgin magazine for me. He said that one didn't need the tweak and KS magazines vary more than he thought. Basically you can't tell the follower is different/odd unless you take the magazine apart.

Also he fired a couple mags, one full auto with no hiccups. All his new builds will get more round tested from now on. I think he shipped it Wednesday.

Edit: added some info/fixed typos (posted original from phone)

Thats good news...ill be waiting for some range reports

EDITED.

Headed to the group pit shoot tomorrow.  As I stuffed the four magazines the whole issue became more clear. I think the problem mainly has to do with the feed lips. First of all the mags have subtle yet detectable differences. The round can hang on the tiniest burr. So first I knocked any burrs off then took the rough feed lip inner surfaces to some semblance of smooth with 600 grit. Eventually will do 1200 then polish, just no time right now. But already the lips are much smoother and manually sliding bullets out and manual feed much smoother, less problem prone, the round doesn't go to one side (hits burr) or straight up, excessive drag on feed lips.

Also of note, RMW hammered the exit (last) portion of the feed lips back in, as they were originally much wider. They "tips" are now actually closer to the original .45ACP configuration.

Can't see much in the picture. Left is unaltered mag. Right is as received from RMW in original altered condition:

(http://pws.cablespeed.com/~pablomail//GGMags1.JPG)

So how did it go? Did your gun run ok?

No.  :(

I will post up when I get rid of that silly pistol tube and have an actual rifle.

Bummer. Are you still having magazine problems?

Not a huge deal. Ron is fully supporting me. I'm just waiting until I can fire it as a rifle. So we wait. On ATF.

All but one of the magazines seems to just right now. One needs the feedlips brought in just a couple thousandths.

Well I got my NFA Tax stamp and have a 10mm SBR.

Well well ....
How does it shoot?

Quote from: sstewart on May 16 2015 11:08:54 AM MDT
Well well ....
How does it shoot?

Can't make it to the range today......and for that matter maybe not until Friday. Ugg........... :o :-[

Yeah it's raining here. Indoor ranges are crowded on weekends.

Quote from: sstewart on May 16 2015 11:08:54 AM MDT
Well well ....
How does it shoot?

It shoots like a dream. What a road trip to get to this point!!!

First the (sorta) bad: I need to fine tune 3 of my 4 Grease Gun magazines. Oh so close. One must learn these magazines. These three had the odd feed issue because the feed lips are just a hair too wide.

The good: The single dialed in magazine allowed the gun to run line a dream. I was actually stunned and relieved at the same time. Oh man, rapid fire HOT 10mm from a 11" barrel? WOW. The gun with the MFT Minimalist Stock and RVG is a super comfortable and shoots very tight groups. It's pretty light so 220 grain bullets push pretty good - I had one or two misfeeds with these bullets, but my Glock doesn't like those largr bullets either. I had zero issues with 155gr and 180 gr. It even shot plinking rounds (I was worried that it could ONLY use hot ammo).

So as for the main cause? In the heat of fighting the thing, I think it was too many variables screwing up at the same time for me to nail down. All I learned so far can be summed up: AR Pistols absolutely SUCK. 10mm very short gas tube AR pistols WILL short stroke like fat guys at a pork chop convention if not shouldered firmly. Once I got the the thing shouldered with a rifle tube, proper spring, the bolt cleaned up and a good mag dialed in, all my worries were GONE. I even shot it like a pistol again, yep misfired the same as before.

Now I can't wait to shoot it some more. What have I created??? ;D :-X :))

That's awesome that you have sorted out the mag issues.
Don't quite get the short stroke thing. 
Haven't experienced that with my 300 blk ar pistol with 12.5 barrel.

Quote from: sstewart on May 23 2015 06:21:42 AM MDT
That's awesome that you have sorted out the mag issues.
Don't quite get the short stroke thing. 
Haven't experienced that with my 300 blk ar pistol with 12.5 barrel.

How long is your gas tube? (serious question)

How strong is your right wrist?  ;D

Gun was catching me limp wristed with that stupid Sig brace even, just never was comfortable shoot the beast as a pistol. Never limp wristed a pistol before, but somehow this combination does it with routine precision as confirmed yesterday.

Probably pistol length. I bought the upper and built everything else. Is yours carbine length?
Still want one of these. 10mm is so much cheaper to reload than 308 or 300 blk.

I had an ar pistol in 5.56 with a 7.5" barrel it ran perfect but looked like a flamethrower

Quote from: sstewart on May 23 2015 07:27:14 AM MDT
Probably pistol length. I bought the upper and built everything else. Is yours carbine length?
Still want one of these. 10mm is so much cheaper to reload than 308 or 300 blk.

Pistol length gas tube is what 6.75"? Mine is just inches long. Like 2" or so. I readily concede it could be me 100% limp wristing. I tried one handed, with and without the brace, two handed,etc. As soon as I went to rifle stock, problem ended. Try pistol hold, starts again.

10mm is a hoot and well worth it.

Quote from: 10mmfan on May 23 2015 07:57:21 AM MDT
I had an ar pistol in 5.56 with a 7.5" barrel it ran perfect but looked like a flamethrower

No flame out of an 11" barrel 10mm!!

People 100% report no issues with pistol AR's and rifle rounds. I searched the web and no limp wristing stories (only Glock 9mm pistols!!). All I know it happened to me. And  as I stated never had any limp wristed problem shooting any other pistol.

Wow the more I fire this thing the more in love I am!!! The cool thing is that it fires plinking light ammo - the reason this is cool is because when Ron and I were working through the issues he kept telling me I needed
super hot ammo to make the gun run and I sort of resigned myself to that. But I can put all kinds of rounds in the magazine and the gun doesn't seem to hiccup. It just want to be a rifle, it's all that it asks. Just a complete hoot to shoot.

  Hola, Pablo,
  Thought you might enjoy reading about my RMW Xtreme 9x25 build.


I finally bit the bullet and with the help 0f Ron Williams of RMW Xtreme built an AR in a caliber I have long felt would make an excellent carbine.  I am attaching pictures of my latest AR chambered in 9x25 Dillon. Ron supplied the upper and I built a Large Glock Quarter Circle 10 lower for the project.
   I have to say that Ron has really made the difference in developing this piece for me and making it run. He is the "go to guy" for D.I. pistol caliber uppers for the AR!  Not only did he locate a 9x25 Dillon ream to use, he designed the gas system to function at the 9x25 pressures. Getting the 9x25 ream was important for me as I wanted a carbine that would have common magazines and ammunition with my G20.  As is to be expected with a project like this there was some "dialing in" to do with the gun initially?   I at first had some failure to feeds and jams, about 6-7 out of the first 50 rounds.  Ron spent a lot of time with me on the phone helping to diagnose the problem and explaining how to fix it.  I just followed his instructions and reported results back to him until the gun was running fine.  Most of the problems had to do with differences between my lower and the one he had used to test the upper with.   Ron is so knowledgeable about AR's he was able to take the info I gave him and explain to me what was going on!   He is a genius when it comes to this stuff!
   The debate I had with myself over the last couple of years was which would make the better carbine, 10mm or 9x25.  While the 10mm is probably the more practical round due to ammo availability I felt the 9x25 offered some advantages over the 10 in an AR platform. The 9x25 and the 10 both develop about the same energy at the muzzle with case capacity being nearly the same. But the smaller bore size of the 9 means better gas availability to operate the Direct Impingement system as well as higher velocity at the muzzle. This, along with the better bullet B.C. of the 9 means a flatter shooting piece able to reach out a little further than the 10mm. I anticipate an effective range in excess of 300 meters with good hitting power at that distance.  In addition, I followed Ron's advice and had him install an adjustable gas block on the gas system.  This has allowed me to dial down the gas to control recoil.  That makes for a very nice soft shooting piece that is easy to keep on target.
  As you can see from the pics, I have kept my 9x25 AR pretty basic. My thought on a pistol caliber carbine is to build as light as possible for better portability and maneuverability. I have attached a tactical scope, which my old eyes almost require lately, and I intend to mount a Magpul BUIS folding rear sight. It's a medium barrel with a 35 caliber hole drilled through it, which makes the barrel fairly light. I have not weighed the piece but believe it comes in just under 7 pounds. Recoil is adjustable with the adjustable gas block so the lighter weight feels good when firing the weapon.   .
So far, I have to say I have been very happy with my decision!  The Dillon is very fast out of a 16 inch barrel and just judging by the way it smacks around various targets at 60 meters I have to say I'm impressed.  This thing will toss a 1 gallon milk jug full of water 12 to 15 feet in the air and about the same distance to the rear!
  I am still working up loads for the AR that will be usable in my G20 as well as the AR but my base load so far has been 10.6 grs. Of Longshot behind a 125 grain bullet.  I do not own a chronograph so I don't have exact velocity figures but I believe that load is producing in excess of 2200 FPS out of the longer barrel.
  This higher velocity has produced a problem of its own though as none of the bullets I have used so far stands up to the higher velocity. I have used ZERO, Hornady HAP's and sierra with the same results. Upon contact with a water jug these bullets immediately disintegrate into BB sized fragments.
  Gold dots seem to do a little better and hold up well enough that you can see they penetrate both sides of the jug.  I also have plans to load 125 gr. X-TAC by Barnes and 125 grain Montana Gold 357 Sig.  The MG has a brass jacket and a harder alloy core that may hold up well to the higher velocity. As time goes by I intend to try other options such as 357 magnum bullets sized to .355.  Should be fun!
  If you are a fan of the 9x25 I would suggest contacting Ron and looking into building a carbine to match your pistol. This little round has more than enough power and velocity to make a great intermediate rifle. So far, my experiment has gone well and working to dial in the piece and come up with loads for it has proven to be more fun than I have had on the range in quite a while!


[attachment deleted by admin]

Wow.  Hot dog!  9x25 AR is definitely on the list. Ron has been getting plenty of mention. A couple issues back Shotgun News did a 9x21 AR from RMW. SEEMS to me a 9x25 would feed better than a 10mm. I  still wrestle with the GG magazines

Mine still has the occasional feed glitch. I have become pretty masterful at manipulating the feed lips so magazine errors are limited. Partial feed errors are more common. The round goes about 75% in, and bolt stops. I do not know the cause of this.

Pablo,
  I feel your pain! I went through the same thing and it is a PITA !  I put a stronger spring on the Mag release bar and that helped a little by keeping the mag more stable. But Ron also said to visually check to see if the two bottom lugs of the bolt were getting good contact on the round as they stepped it from the mag .  My problem turned out to be that due to a change in the design of the Glock mags the two bottom lugs of the bolt were making contact with the metal on the rear of the Glock mags. My mags set a little higher in my lower than Ron's did in his lower.  The lugs making contact with the rear of the mag was         " jolting" it just as the round was being fed to the chamber, causing the FF's .  I took a Dremel and small stone and ground just enough of the side lugs off to insure they cleared the mag. I did not shorten the lugs, just narrowed them by about 30%. They have to be long and strong enough to strip the round. This solved the problem for me.
  My experience may be different than yours because I use the Glock mags and your using the GG's I believe. But it would be worth visually checking it out.

Good place for me to start. Thanks!

Good luck Pablo.  Once it all comes together you'll fall in love with it!

It is fun regardless. It would stop once or twice in a magazine of 32. I finally played with the sights. Great fun was had. Two clicks brought it exactly to the exact left side of the target where I was on the right. One click right and centered. Shoots and holds quite nice. Shot some steel at 200+ yards.........that's challenging!

Also it stove piped 2-3 times. Seems like would be bolt issues. It actually ran really well on light ammo, contrary to what Ron was thinking. But hot rounds didn't cause any issues. The SBR is so light now, I can really feel the difference in ammo.

Damn Pablo, now you've got me wanting a 10mm SBR to go with my 9x25!  I need to give my bank account a chance to recover, but it's deffinately something I want.  You are absolutely right, these builds are about the most fun you can have at the range and that includes tweaking them to make them run. Just part of the fun and good learning experience also.  My 9x25 appears to be very accurate also. I think the long barrel and high rate of spin due to velocity does wonders to stabilize the short pistol bullets.  Have not had a chance to shoot mine over 100 yards yet but will soon.
  Reading your last post, something occurred to me.  The 9x25 does feed a little easier due to the smaller diameter of the bullet, this is true in rifle or pistol. But one thing I have become aware of in my 10mm pistols over time is how critical the overall length of the round is in feeding properly. Generally, the shorter you make the round, the easier they feed. This varies according to bullet styles and model of gun but is something I record for each load to avoid feeding problems.  Stovepiping is sometimes an indication of too much length on the round.
  It occurs to me that the same thing is probably true for rifles so I am wondering if you re-load and if you've experimented with O.A.L. Of your rounds? 

Something occurred to me when I was cleaning the gun this AM. When the gun has a FTFeed (partially in chamber) and the round can go the rest of the way into the chamber (manually shake gun or feed assist) the trigger is NOT set. Would this not indicate a short stroke event which didn't latch the hammer? I feel when it happens so I don't pull the trigger prematurely but for sure when the bolt is closed the hammer is already released. Like I said this happens on average every 15 rounds or so, and does not matter - hottest or mildest ammo. I am at a loss as to cause.

I agree how some 10mm guns are susceptible to very minor ammo differences. Other than some Underwood 200gr that had some interesting bullets that really didn't feed worth a darn in anything, the issues don't really seem to follow ammo type - and all my loaded ammo  is well with specifications and I am pretty anal. In fact I was shooting up a bunch of very HOT JHP 155gr ammo and it fed quite well, and to back what you say, it had more issues with 200 and 220gr factory ammo.

Also see my posts about my Glock 20L with very tight 6.2" 10mm Lone Wolf barrel (chamber) (oh and I have a 6" 9x25 barrel for the G 20 as well)

Sounds like you may be short stoking. If you have the adjustable gas block you can dial it up a little to increase the stroke. If not, you might try over-lubricating your weapon until you get it broke in.  As a rule,on any new semi auto I buy I always use a lot of lubricant until the parts are broken in. My reasoning is that when the parts are new you are actually lapping off minute particles of metal as the weapon breaks in.  You want these to float off the mating surfaces to allow for the break in to create the smoothest possible surface.  Lube the rings on the bolt well and dry cycle a few times before firing and make sure the breaks in the rings do not line up with each other to cut down on gas leaking through them.  All this will help the weapon cycle with less gas. After break in you can adjust for minimum recoil.
  I will check out your posts on the lone wolf g-20 barrels. My experience is that the lone wolf chambers are much tighter and better supported than the stock Glock barrels. Full length re-size Every round or you can have problems with the rounds feeding into one barrel and not the other. It does not sound like your rounds are too large for the chamber since you can easily tap them in using the forward assist.  One thing you need to check with both re-loads and factory rounds is the area were they are crimped. Too much crimp can easily bulge the sides of the round just behind the case mouth and this can cause the kind of partial feeds you are experiencing .  Have fun!

Interesting comment on the lube. Very interesting!

Being a lube guy, I think the same thing about lubing and break-in. So I figured I was past that step by now, so believe it or not this time I was running a bit dry - AND this AM when I took the upper off and tried to pull the bolt out - IT was stuck. Stuck hard. I cleaned the gun really well, and really lubed it well, even dipping the ring end of the bolt in synthetic (Amsoil) ATF (no VII's or polymeric thickeners). Wetted the rest of the carrier and such pretty well, bolt face dry.

Suspect my chamber is probably a bit tight. That's not helping.

Oh and you might also be onto something with thinning the lugs a bit.

Like any good problem - a combination of things!!

Pablo, 
  My biggest wish is that my suggestions are helping, not hurting!  If so, I am happy.  And, let's face it, what I learn from your experience  will no doubt come in handy when I build a 10mm.
  Let me know how it turns out!

Helping. So far good ideas. Wish I had a range in my yard to try it out with the ultra lubed bolt. It's the only variable I changed this time.

Milli-tech lube helped my 12.5 inch 300 AAC AR cycle subsonic rounds, So it sounds like that could be helping you too.
208 gr. amax.  H110 I can't remember the exact powder load. It was a couple tenths below book max. Was definitely short stroking until I lubed it.
No suppressor is allowed in this state.

Going wet this time!

Pablo,
   How's your 10mm running? Did the lube help?

Quote from: mrpipesmkr on August 08 2015 01:52:17 PM MDT
Pablo,
   How's your 10mm running? Did the lube help?

I won't make it to the range until Friday at the soonest.

Quote from: Pablo on February 26 2015 03:49:37 PM MST
Here is the completely finished upper (well I still need to Loctite things):

(http://pws.cablespeed.com/~pablomail//FinishedUp.JPG)

What length of barrel is that? 10.5 or?

11". It's in the OP.

Quote from: mrpipesmkr on August 08 2015 01:52:17 PM MDT
Pablo,
   How's your 10mm running? Did the lube help?

Lubing every moving part helped a bit but problems not completely solved. It was pretty juicy. Cleaning sure was easy though.

Mainly the short stroking remains. Even the hottest high pressure 10mm loads it happens. It's frustrating because it's not frequent, seems to happen more when I fire rapidly though.  I think the fact the brass is pitched 1-2pm (1pm mostly) is another clue.

What next? Buffer and spring. The more I read it comes down to being under gassed.

My buffer is a 3.0 oz carbine buffer. It looks normal. I knocked the pin out, insides normal. I took two of the steel slugs out and replaced them with 1/2" OD oak dowel cut to ~0.6" long. Finished weight is ~1.8 oz for the buffer now.

Will try soon.

Next I have ordered this lightweight spring: http://www.davidtubb.com/ar15-tubb-parts/ar15-buffer-spring-stainless (http://www.davidtubb.com/ar15-tubb-parts/ar15-buffer-spring-stainless)

I was talking about this lube: ( not lube in general)
http://www.militec1.com/miva/merchant.mvc?Screen=PROD&Store_Code=militec1&Product_Code=BONUSPAK&Category_Code=1 (http://www.militec1.com/miva/merchant.mvc?Screen=PROD&Store_Code=militec1&Product_Code=BONUSPAK&Category_Code=1)

frustrating for sure. The lube is above is great. You can shoot gun to generate the heat to penetrate the metal parts or bake metal parts in oven. (my wife would freak out about that part)

The Tubb buffer spring arrived. VERY nice flat wire spring. I think I may get the standard versions for my 5.56 and 6.8SPC.

Going to the range tomorrow with various springs and buffers. Looks like perfect weather.

The spring worked great. Buffer weight didn't seem to matter.........or did it.......more later........

Such a teaser .....

I don't have a ton of time to type, so some amount of trust will be necessary from the reader, that I indeed was somewhat scientific about trying the springs and buffers.

Gun oiled up pretty good with CorrosionX only.

Target at 30 yards. Not precise shooting, standing.

Basically I loaded up 2 magazines (with slightly different feed lips) with 5 rounds each of 180gr medium hot rounds. More or less my standard. Started with my light 1.8oz buffer and Tubb flat spring. All 10 rounds fired flawlessly. Next 10 rounds in each. 20 rounds flawless. 15 in each, 30 flawless. WOW 60 rounds, no issue. Call a cease fire, pick up the brass all in a 2 foot circle, 5-6 feet ahead at 1 o'clock. So then I yacked with the one other guy at the range at 8:30AM, gun cooled down, maxed out the magazines (32 rounds) - first round, fails to go into battery. Hmm....

So I stop, clear, offload the magazines to 5 rounds and try again.....maybe 1 every 4-5 rounds, fails to fully seat in battery. My thoughts are racing a bit, thinking dirty tight chamber, etc....

I swap to H buffer 3.8 oz, gun behaves exactly the same. Try other ammo, try one minor tweak of the feedlips on one mag. Same behavior.

I come home, pull the carrier and the bolt just barely moves in the cylinder and it's dry as a bone. Never felt a bolt so grindy tight

Quote from: Ron Williamsif you lube the rings on a pistol cal the hot gasses stick to the rings & will slow it down. Just run them dry on the 10mm.

RMW Xtreme

I'll just leave that here.........

(http://pws.cablespeed.com/~pablomail//911Target.JPG)

To summarize:

No stovepipes, no failures to extract. Locked back as expected when bolt lock button held.
I will stay with the light flat buffer spring designed for pistol caliber carbines and I will use the standard 3oz buffer.

Multiple rounds fired with no issue, gun cooled down, bolt become almost impossible to move as a piston. Most likely a lubricant issue.

I detail cleaned the bolt and carrier spotlessly. Reassembled with no lubricant. It seems relatively tight compared to my other AR bolts, but will not attempt any mechanical fix. Took carrier apart again and soaked ring area, and carrier in 2 stroke engine oil. Reassembled very wet and the bolt seems to move freely enough. Next trial will not change other variable and will see if some type of seizure occurs when gun cools and reheats. May remove bolt carrier during trial.

The thoughts for the 2 stroke oil: It should prevent rings from sticking in cylinder with heat and force. We shall see!

Frankly, for lack of better words, the gun now feels badass. Light (around 5 pounds), easy to shoot, and accurate as I want it to be. Fun project!

Pablo,
  Just a quick thought. It sounds like your bolt and rings are too tight in the carrier. The rings, when inserted into the carrier completely close the gap that each ring has prior to insertion. Forcing the bolt into the carrier gets the rings in but leaves less than zero tolerance. With the lube burned off by firing the weapon the bolt and rings seize up.
  If this is the case firing the weapon enough will eventually break it in, but this might prove to be very frustrating and time (and ammo) consuming.
  You might try lapping the rings to mate them to the carrier with a tolerance loose enough to move freely but tight enough to allow the gases to function the bolt.
  Ther are several polishing compounds used by gunsmiths to lap parts together to insure a perfect fit but I have found that Turtle Wax polishing compound is available in most automotive parts stores and works well.  Just remember that you want to use the white polishing compound that comes in a green container, not the rubbing compound that is red and comes in a red container.
  Put some of the compound on the rings, insert the bolt into the carrier and work the bolt back and forth until it loosens up. Make sure the gaps in the rings are not lined up and change their positions each time you refresh the polishing compound on the rings. Do this until the bolt does not seize in the carrier but still requires some effort to move. Test fire the weapon and repeat if needed.

Quote from: mrpipesmkr on October 03 2015 03:07:16 AM MDT
Pablo,
  Just a quick thought. It sounds like your bolt and rings are too tight in the carrier. The rings, when inserted into the carrier completely close the gap that each ring has prior to insertion. Forcing the bolt into the carrier gets the rings in but leaves less than zero tolerance. With the lube burned off by firing the weapon the bolt and rings seize up.
  If this is the case firing the weapon enough will eventually break it in, but this might prove to be very frustrating and time (and ammo) consuming.
  You might try lapping the rings to mate them to the carrier with a tolerance loose enough to move freely but tight enough to allow the gases to function the bolt.
  Ther are several polishing compounds used by gunsmiths to lap parts together to insure a perfect fit but I have found that Turtle Wax polishing compound is available in most automotive parts stores and works well.  Just remember that you want to use the white polishing compound that comes in a green container, not the rubbing compound that is red and comes in a red container.
  Put some of the compound on the rings, insert the bolt into the carrier and work the bolt back and forth until it loosens up. Make sure the gaps in the rings are not lined up and change their positions each time you refresh the polishing compound on the rings. Do this until the bolt does not seize in the carrier but still requires some effort to move. Test fire the weapon and repeat if needed.

THIS. This exactly had crossed my mind. I am actually super grateful you posted, because there is pretty much no doubt I would have started with something too aggressive if all it takes is car paint/clear coat polishing compound.

No problem Pablo, I hope it solves your problem.  I have used this same product on rough bores and with patience it works well. Even chromed bores can be improved this way although it is important to avoid polishing in the area of the crown too much on any bore.
  Your carrier is probably chrome lined also and will resist wear.  The rings will probably wear a little quicker which is what you want. Have fun and let us know how it goes.

So I compared the feel of the bolt in the carrier bore with my 5.56 and my 6.8. The 10mm is much rougher (not even close) and does have a sticky point. So I tried the polish. First of all it started pretty rough with the polish as the only "lube". But it got easier, and the rough beginning sort of broke through. The absolute most amazing thing? The amount of metal flakes and crud that flushed out!  :o REALLY SHOCKING!! After that I triple cleaned it, blew it out then flushed with spray lube. Super clean now and re-assembled with 2 stroke oil on the rings. WOW, it's piston gas tight feeling but nice and smooth.

I actually think the lube and rings were allowing the rings to move over this junk - but the polish didn't allow this and just took the stuff out.

Not sure when I can take the gun out.

Good news, Pablo!  It sounds like you might have solved the problem. I can't figure out what the metal flakes were but no doubt they had something to do with the bolt being so hard to move. When you look into the bore on the carrier does it appear to be smooth, not pitted or rough? As long as your rings are intact and the bore is now smooth it should function.
  Let us know how it works.

It's very smooth looking now with light and magnification. The odd thing when I looked in before it was kinda of rough, .........but maybe I was in denial, assumed it was "good enough" and didn't really inspect it to start (wish I would have)

I have to think the metal (and black) flakes were in the carrier bore. I didn't physically touch anywhere else. If this doesn't completely solve the problem, I think it really puts one more item in the works better than designed column! :D

I think that if the bolt feels similar to your other AR's and moves freely you have probably solved the problem.
  I don't know what the debri you got out of the carrier might be , I've never seen it before. Do you know if the flakes were magnetic? That would indicate  they wee steel or at least iron based. Perhaps metal shavings that were not cleaned out of the carrier barrel prior to it being chromed. Most chrome is black before it is buffed to a shiny finish. It's possible the company that manufactured the carrier just didn't get it cleaned out before finishing it.
  Of course the debri you got out of the carrier could be carbon from the discharged rounds. It doesn't seem to me that you have fired the weapon enough for that much carbon build up. It is possible that the lubricant you are using is creating the carbon when it gets hot and cookes down. You might try a different lubricant.

Not magnetic, but the shiny bits and some dark bits are metallic. Some is carbon as well. I've used many lubes, and I'm sure some did coke, plus some is powder residue. I'm pretty sure with the amount of synthetic lube used some of the times, the rings rode right over the junk. Not so worried at this point, cleaned up nicely.

It does sound like you've got the problem solved, as long as the bolt moves freely you should be OK.  Le us know how it works at the range!

 :)) With this thing it is indeed A problem solved. Next!   :-\ ;D

Quote from: sstewart on September 07 2015 08:59:41 PM MDT
I was talking about this lube: ( not lube in general)
http://www.militec1.com/miva/merchant.mvc?Screen=PROD&Store_Code=militec1&Product_Code=BONUSPAK&Category_Code=1 (http://www.militec1.com/miva/merchant.mvc?Screen=PROD&Store_Code=militec1&Product_Code=BONUSPAK&Category_Code=1)

frustrating for sure. The lube is above is great. You can shoot gun to generate the heat to penetrate the metal parts or bake metal parts in oven. (my wife would freak out about that part)

Update: I ordered the Militec.

I came to the conclusion the supplied rings were just junk. I made them smoother, but they were still rougher than my other AR's, PLUS compared to 5.56, and 6.8, a 10mm AR is undergassed no matter what. It has become an unavoidable statement of physics. SO, I installed JP Enterprises gas ring. HOLY SMOKES sweet with even low lube. Will get the Militec and then chute it.

The real thing here is that making a 10AR is NOT some easy project.

Pablo,
  I thought I would share a write up i did on the 9x25 AR and 10mm AR I had Ron build for me. The bolt rings he supplied with both builds were fine.  I'm wondering if you got a bad round or something which blew debris into the bolt. I have found that I have to load medium hot rounds for the 10mm, especially while breaking in. It will loosen up though. The 9x25 has plenty of gas for the DI system.  I also would say I highly recommend the Quarter Cicle 10 lowers for you next build.


  I thought as long as I was logged on I would update some information on the 9x25 AR 15 D.I. Carbine I purchased from Ron Williams at RMW extreme as well as A 10mm AR I had him build. I want to give my impression of both calibers and my experience with them so that anyone considering such a build will have the info available.
  Here, I guess I have to go ahead and admit that I must be a 10mm nut!  Including the 9x25 variant I own four now and am impressed with all of them!  The flexibility of the 10mm is fantastic. With carefull work up and the right powder it can be loaded to velocities that exceed book max and show minimal pressure signs. For plinking it can be downloaded to 40 s&w velocities and maintain accuracy and function in a pistol. Throw in the 9x25 variant and you have a round that can be tailored to achieve a lot of different things.  Pretty hard to beat!
  First of all, both of my carbines are built on Quarter Circle 10 large Glock lowers. I went with this lower for both my builds because I wanted to have magazine compatibility with my Glocks.  Overall, I am very impressed with the Quarter Circle 10 lowers. They are billet machined lowers and both the machine work and the finish are excellent. They feature a proprietary mag well and mag release and are the only lowers I am aware of that have the bolt hold open on the last round. The bolt hold open is a little touchy to adjust but once it's dialed in is a nice feature.  The Quarter Circle 10 company also is one that stands behind its products. The first lower I got from them had the magazine set too low in the magwell which tended to cause feeding problems. After being informed of this problem Quarter Circle changed the design to raise the magazine and gave me a no hassle exchange of my original lower for a new lower with the raised magazine.  Quarter Circle paid for all shipping to complete the exchange, you can't ask for more than that. The new lower feeds much more reliably in fact has few failures of any kind, and I highly recommend these lowers compared to others I have seen.
  The first of these carbines I built was the 9x25 Dillon. I love its parent cartridge, the 10mm but when considering a carbine with a 16 inch barrel, it seemed that the better SD of the .355 bullet as well as its higher velocity would  make for a better all around carbine. After playing with the 9x25 for awhile and comparing it to the10mm I have to say that these considerations of mine have remained true. The 9x25 round loaded with a 125gr HP and a semi hot powder charge that I can comfortably shoot out of my Glock 20 exceeds 2000 FPS and may reach the 2200-2300 level.compared to the 10mm it is flat shooting and will still retain usable energy beyond 400 yards. I have an adjustable gas block on this AR and dialed in properly it will reliably extract brass and drop the empties right at my feet. 
  The 10mm carbine is a great rifle also, but here we are looking at pushing a 180gr bullet at 1700-1800 FPS. The lower velocity along wit the poorer SD of the bigger bullet means that this carbine does not shoot as flat as the 9x25. Going to a slightly heavier bullet would undoubtably extend the range a little but I believe it would still be limited to an effective range in the 250-300 level. But it has to be said that this round has an unbelievable punch at close range!
  It stacks up like this, for hunting, if you hunting grounds are fairly open you would prefer the 9x25 for that occasional shot were you have to reach out  a ways to bag your deer.  In brush country were range is limited the 10mm is going to bust brush better and deliver a larger bullet for a quicker kill. For hunting hogs, which is usually done at closer range the 10mm is probably the best choice. In combat situations the 9x25 would clearly give better all around performance but if you were room clearing the 10mm would be the way to go.
  Using the Quarter Circle 10 lower, both of these rounds feed reliably from 15 round Glock  magazines. I have not tried extended mags such as the Kriss's mag extensions but will in the future. Of course there is always the hope that Glock will come out with 30 round mags for the G20.  For now I don't mind using the 15 round mags as they are less awkward and it is easier to use them from the prone position.
   Both rounds, 9x25 and 10mm, cycle in the DI AR15 format with the 9x25 providing plenty of pressure due to the smaller bore. The 10mm works also but due to the larger bore must be loaded to at least a medium level with lighter bullets requiring a semi hot load. I have used Longshot powder for my carbine loads in both calibers and it seems to work well, slow burning with a good pressure curve. There are other powders which I'm sure would work in these cartridges and I hope to try them in the future although Longshot is hard to beat in a 10mm case.
  Recoil on both carbines is very manageable with the 9x25 being somewhat less than the 10mm. This is at least partially due to the adjustable gas block I have on the 9x25 but the larger bore and heavier bullet of the 10mm sort of dictates a more solid thump to your shoulder from that piece. Really the recoil on both is just enough to increase the fun and let you know your shooting something. Both are very easy to hold or return to point of aim and the 10mm with a red dot will put a series of shots on target in pretty short order.
  I'm very happy with both carbines and have had a ton of fun experimenting with them.  If your a 10mm-9x25 fan and have considered a PCC  I would suggest looking into RMW extreme  (Ron Williams) and Quarter Circle 10. You won't regret a carbine in either of these calibers.

I think you are somewhat correct on thinking it's the gas system fouling. Ron says to run it dry, try as I might I can't run an AR bolt dry. What do you lube your bolt with again?

The rings under magnification looked nasty. All chewed up and rough. The bolt tail was crusty when I received it. So I cleaned and polished the tail. With the new single piece "ring" it is now SMOOOOTH. Will lube with the Militec. Probably not the cause of all my problems, but a start. I'm gonna bring  two types of ammo for the whole range trip. Start with one factory type it liked - I'm pretty sure the gun seems to like Sig. Then maybe change to one other and see what happens. Problem with some factory 10mm ammo is I don't know what powder was used.

9x25 would probably would help. And QC-10 probably is a more reliable lower, knowing what I know now. It's darn frustrating, but everyone needs a hobby!

I use two lubes for my AR,s.  One is a CLP ( cleaner lubricant preservative) #S758 I got while in the military. I'm about out of it so I've been using Break Free CLP that I got from MidwayUSA also. Both seem to work OK.  The Miltec should be OK.
  I'm wondering if you need a new bolt carrier, is it smooth inside where the rings run? You might check with Ron and see who supplies his and if you can exchange.
  I will say that with the 10mm the gas port is closer to the chamber than the 9x25 so getting debris from fired rounds is more likely. I use reloads with Longshot powder which seems to burn clean. Also, my rounds aren't as hot as I can go but are hotter than factory which probably means a cleaner burn and more pressure.
  Also, I did initially have some partial feeds from new, full, Glock magazines. Forward assist generally took care of them and I attribute the problem to the action and the clips not being broken in. I'm wondering if you're longer mags arn't title enough too slow down the action?
  Let me know how your range trip goes.

He says nothing wrong with the bolt carrier. I haven't bugged him for awhile. Basically he said it worked for him.

How long IS your gas tube on the 10mm? Mine is super short. The gas hole is right after the chamber.

Quote from: mrpipesmkr on December 23 2015 12:23:35 PM MST
  I'm wondering if you need a new bolt carrier, is it smooth inside where the rings run?

It looks smooth, and moves as smooth as my 6.8 bolt assembly that is on my bench. It certain moves with less force than the 6.8.

Quote from: Pablo on December 23 2015 12:47:07 PM MST
He says nothing wrong with the bolt carrier. I haven't bugged him for awhile. Basically he said it worked for him.

How long IS your gas tube on the 10mm? Mine is super short. The gas hole is right after the chamber.

Mine is probably where yours is, Ron uses a program to determine where to place the port to get enough pressure to run the gun.  He's done many 10mm's so he's got the location down pat.  The bore of the 10 being large means it has to be closer. But most experts will say that the majority of the powder is burned in the case before the bullet gets down the bore very far. The expanding gases then drive the bullet down the bore.  The fact that I reload may be the big difference here. My typical load is 9.6 grains of Longshot under a 180 grain bullet. I use a standard primer but have tried mag primers with this load which makes it pretty hot as the powder burns quicker. You might try reloading some rounds to see if this improves thing. If you don't reload, perhaps you know someone who does.
  Another thing to try is locating some 200 gr loads to try. The heavier bullet, loaded to the same power level usually means more pressure .  When you purchase ammo, look for the hottest loads you can get. Most 10mm you buy off the shelf is pretty anemic, more like 40S&W loads. I would suggest googling Underwood and Double Tap ammo, both of which load HOT 10mm rounds.  Call or email them and see what they have in 180-200 grains loaded with Longshot Powder.  They are good people and will work with you!  I'm only saying this cause it seems to run mine OK.
  If you don't reload Pablo, I would suggest you look into it.  It's a great hobby, cuts your cost over time, and when you get into it you learn so much about ballistics, pressure curves ect.
  Look up Underwood Ammo (the hottest, I think) and then Double Tap and let me know what you think.

I do reload. And I have Longshot powder. Maybe next week I can carve out a few hours.

Quote from: Pablo on December 23 2015 01:33:04 PM MST

Quote from: mrpipesmkr on December 23 2015 12:23:35 PM MST
  I'm wondering if you need a new bolt carrier, is it smooth inside where the rings run?

It looks smooth, and moves as smooth as my 6.8 bolt assembly that is on my bench. It certain moves with less force than the 6.8.

Your carrier should be OK then.
  On my previous post I forgot to mention my thinking on the hotter loads.  With slow burning powders typically used in 10mm running them at lower pressure does not give a complete burn and usually means a dirtier chamber and gun.  With slow powders upping the pressure promotes a more complete, cleaner burn.
  You may just be fighting the partially burnt powder clogging your bolt and rings. I have no doubt a hotter round will create less unburnrd powder. I suggest Longshot only because it does well in 10 mm and has been working for me in my build.
  I just saw your post that you do reload. Great! Work up some Longshot loads and see if they make a difference.

I have shot Underwood, Buffalo Bore and Double Tap.

They all shot fine.

Then I cooled the rifle down, came back to shooting and jammomatic.

I have shot medium home loads, and yes the whimpy commercial stuff. Sometimes it works, sometimes not.

The best luck I had was with the new Sig 10mm. 180 grain. Then I switched to some other ammo, ran fine, cooled down and ran like junk again.

I think you are very close, it builds up and when cooled, really cokes up and can't unfowl.

Pablo,
  Sorry you are having problems with your 10mm build. Keep working at it, I think you have shot it enough to know the 10mm carbine is just a real hoot to shoot!
  As near as I can tell, our to builds are the same except fo 3 differences. 1. Mine is a 16 barrel, yours is, I believe 11 inches.  2. I am using Glock 20 mags and you are using Greese gun mags. 3. I use hand loads exclusively, no factory ammo. You have used a mix of different Ammos.
  Considering the location of the port in our rifles, barrel length should not be an issue. The system is pressurized in both our carbines well before the bullet exits the bore.
  The "stiffness" of the Greese gun mags could be contributing to the problem but this should be avoidable by partially loading the mags, rather than fully loading them. As I have mentioned, I have had a few partial feeds from new Glock mags but as I've worked with the piece it has loosened up and this problem is going away.
  So, it appears to me that the biggest difference might be the ammo we are using. You problems seem to be centered around carbon fouling rapidly building up on the bolt and rings slowing the action down until it quits working. I have not had this problem and I've shot as many as 50 rounds from mine in one setting. I do have carbon build up as al DI weapons will, but it does not jam the action. I can't say that I have conscientiously let the weapon cool as you have but my feeling is this would not make a difference on my piece, it just seems to run ok even after letting it sit for 15 minutes or so between strings.
  My suggestion then is that you load up some 180 grain Longshot loads working up to 9.6 grains with standard primer. Clean the carbine thoroughly before testing and do not mix any other types of ammo in with the Longshot loads. It's just possible that some of the ammo you are using is only getting a partial burn on the powder creating lots of fowling that you system cannot handle.  My Longshot loads burn pretty clean and the carbon they do create is very fine and not too sooty. The carbon builds up to a certain extent but does seem to self clean a little bit as the fine particles are blown out the vents on the side of the bolt carrier through the ejection hatch.
  The load I use, 9.6 grains Longshot under a 180 gr. Hornady  HAP  billet is  .1 gr. above max in the Hodgdons reloading data, but I consider it to be a medium hot load. The Hodgdons top load of 9.5 grs. Only gives , if I remember correctly, about 33-34000 pounds of pressure. This is way below the 37500 max pressure for the round. Even my 9.6 load does not hit full pressure and I have worked up as high as ( if I remember correctly, don't have my notes available)10.4 grains with a standard primer. At that level I had significant signs of pressure and feel that load is too hot.  9.6 grains with a magnum primer is very hot also, more than I want to run consistently, although Double Tap sells a 180 gr load of 9.5 with a magnum primer .
  The whole point of all this is that getting good pressure in the correct curve Is essential for the DI system. What works in my build may not work in yours. You must have enough powder in the case to create sufficient gas to run the gun. If my 9.6 load doesn't run yours you might try changing the curve by lowering the charge slightly but switching to a magnum primer, thus speeding up the burn and changing the curve.
  Hope I havnt bored you with all this but sometimes listening to another person air out their thoughts will help stimulate yours. I know you are pulling your hair out over your build and hope I am helping. I think when you get it figured out you will be surprised at how simple the solution was!
  Oh, let me throw in a Merry Christmas and a Happy New Year !!

   

Extremely helpful. I won't have time until maybe next week to load. I may just do 50 with 9.5 and 50 with 10 gr. of Longshot. I have plenty of clean 10mm brass, so that's a bonus. I just need to re-setup my press.

Also, absolutely the GG mags never work when I jam 32 into them. I gave up on that long ago.

I think I have the bolt assembly about perfect. One last tweek. I also want to wait for the Militec to arrive.

Thanks a ton!

The last difference I had in the 10mm in the bolt carrier group (from my 6.8 and 5.56) was the very tight, say sticky, firing pin.

First let me say I have spare bolts and firing pins and other parts for my other AR's. So I have parts to try things out. That said I took my known well functioning BCG's apart one at a time and brake cleaner degreased them, twice. Zero lube. Then reassembled. Somewhat key when comparing the feel. The 10mm is now the smoothest, but when the firepin was manual pushed into fire mode, it would hang and not fall back as the other two would. And only would retract with some level of effort, which I found disturbing. All parts are very clean. I know this shouldn't have any real effect on my issues, but it was different. So a grabbed a known good spare (like new) firing pin and now the 10mm BCG is essentially the same as my other two.

I will Militec all three when the lube arrives. I just think this variable should be somewhat in control.

I am getting good but not 100% perfect results with PC 180gr Bullets. Using only 9.1 gr of longshot.
I am using quarter circle lower. Dremeled the Glock mags out a little to give bolt space to feed.
Getting an occasional FTF on KCI 45 long mag. 0 to 1 per mag. Mostly 0 on 15 round Glock mags

Quote from: Pablo on December 24 2015 08:59:33 AM MST
Extremely helpful. I won't have time until maybe next week to load. I may just do 50 with 9.5 and 50 with 10 gr. of Longshot. I have plenty of clean 10mm brass, so that's a bonus. I just need to re-setup my press.

Also, absolutely the GG mags never work when I jam 32 into them. I gave up on that long ago.

I think I have the bolt assembly about perfect. One last tweek. I also want to wait for the Militec to arrive.

Thanks a ton!

Pablo,
  Sounds like a plan!  The only thing I would emphasize is, work up to the 10gr load. That is pretty hot and each chamber is different so make a ladder in.1 or .2 grain increments to be safe.
  Also if you have magnum primers, drop down a few tents of a grain and load with the hotter primers to speed the burn. This woul create more pressure at the port given that it is close to the chamber.
  The situation with your original firing pin is unusual.  I wonder if you had debris blow into the firing pin tunnel from the bolt? Something has to be causing the obstruction. You might use a pick to see if you can scrape anything out from behind the bolt face. While this may not be the cause of your problem it may contribute to it. I would also be worried about slam-fires if the pin does not retract. Also, is it possible the pin is bent? This may cause it to bind.
  Let us know how the new loads work!
 

Quote from: sstewart on December 24 2015 02:08:48 PM MST
I am getting good but not 100% perfect results with PC 180gr Bullets. Using only 9.1 gr of longshot.
I am using quarter circle lower. Dremeled the Glock mags out a little to give bolt space to feed.
Getting an occasional FTF on KCI 45 long mag. 0 to 1 per mag. Mostly 0 on 15 round Glock mags

Stewart,
   Thanks for the feedback on your build. It sounds like it is very similar to mine in terms of running without problems. I have not run mine as low as 9.1 grains behind the 180 bullet but feel it might possibly run with that load, especially with a mag primer. Have you tried a hotter loading in yours? It might  help eliminate the FTF problems you are having since they are minimal at most. Also the bolt and barrel are built to handle higher pressures and those higher pressures might promote a cleaner system.  Remember, some .556 military loads generate in excess of 60,000 pounds of pressure.
  I trimmed the lower bolt lugs on my bolt to make them thinner so they clear the metal at the rear of the Glock mags. Still enough lug there to strip the round and lock the bolt without having to alter each mag.
   When you squeeze the KCI mag lips together to hold the 10mm round it lowers the position of the first round enough to cause problems. I gave up on mine, using them on my first QC10 lower they were very problematic. Now that QC10 has replaced my original lower with one that holds the magazine in a higher position I will have to re-visit the KCI mags.  My real hope is that Glock will offer a 30!rounder at some point.  Really, I don't mind the 15 rounders as they are less awkward than the longer mags, especially when firing from the prone position.  I would try the Kriss extensions but find it hard to pay 70.00 for a magazine!
   One last question, do you find your Longshot load is burning clean?.  How bad is the build up in the bolt area?

Quote from: mrpipesmkr on December 24 2015 03:11:59 PM MST
Pablo,
  Sounds like a plan!  The only thing I would emphasize is, work up to the 10gr load. That is pretty hot and each chamber is different so make a ladder in.1 or .2 grain increments to be safe.
  Also if you have magnum primers, drop down a few tents of a grain and load with the hotter primers to speed the burn. This woul create more pressure at the port given that it is close to the chamber.
  The situation with your original firing pin is unusual.  I wonder if you had debris blow into the firing pin tunnel from the bolt? Something has to be causing the obstruction. You might use a pick to see if you can scrape anything out from behind the bolt face. While this may not be the cause of your problem it may contribute to it. I would also be worried about slam-fires if the pin does not retract. Also, is it possible the pin is bent? This may cause it to bind.
  Let us know how the new loads work!

I have shot super hot ammo in the gun with no issues with overpressure, but working up to it makes sense. It's the right thing to do.

I don't have magnum primers. I'll add them to the to do list.

The firing pin thing was resolved by putting a spare pin in - nice and loose like my other bolts. The bolt is exceedingly clean. Trust me on that one. Eventually I will measure the pin I took out, but it did not appear be bent with a simple roll test.

Pablo,
  Merry Christmas !  I hope Santa brings you a cure to your FTF problems for your present!
  Working up to hot loads is always the best idea. I think 10grs with a standard primer and correct COL wil not be a problem for you but you never can tell.
  The reason for the mag primers is just to change the pressure curve to something that peaks quicker. You may find that the standard loads work fine and won't need to mess with the mag primers.
  I'm curious about your firing pin situation. Something has to be different with the old pin versus the new one or they would both run the same. Since you found plenty of evidence of debris build up in your bolt and carrier it seems logical that could cause the firing pin to begin to jam. Scraping a little to see what's in there makes since because some fouling won't be removed with solvents and has to be scraped. With what you've been going through taking a few minutes to be sure there is no build up is just good insurance.  I know you want to cover all the bases.
  I've followed your problems with the build so closely that I think I will be as excited as you when you get it running !  In a way, your problems have been a good "school" for me and I've learned a few things along the way. I appreciate you sharing your problems with the board for that reason!

The bolt is clean. I took it all apart and even scraped inside with a right angle pick that will reach all the way through when the extractor is removed. It's clean.

And I whipped out my micrometer. The replacement pin actually is (slightly) larger OD than the stock pin............so I am baffled.......The replacement pin goes in loosely and rotates freely.

Wait, but the original pin is loose sometimes, tight others........it is indeed ever so slightly bent! I can see it when I clamp the bolt and rotate the pin fully depressed. Nice. Very, very subtle. Does the same thing in my other bolts. Never had a bent AR firing pin before.

  It was just logical that there had to be some difference between the old firing pin and the new one you installed. 
  I have never seen a bent AR pin also. Strange, I wonder what caused it?  Anyway, replacing it has to be a plus.  Hopefully the gun will run a little better with the new pin. I don't think it was your whole problem but it had to contribute to it.

I just started wishing I had a dial indicator, v- blocks, something.........then it hit me, the top my little precision vise jaws. The pin is ridiculously bent! I thought it was subtle because I was mentally canceling out any methods I was using to spin it, chuck it up, etc. It's actually embarrassing now - that I didn't notice this from day one! Trust me, I did nothing to bend this pin (well unless it was ancillary jam damage) . I agree, this wasn't the sole problem, but yet another symptom of this crap bolt assembly.

Quote from: sqlbullet on February 27 2015 02:20:10 PM MST
I really wanna see them argue in court that a you become a felon based on how you hold a gun.

:))  ;D  ;)   8)  :P   
It's an unconstitutional agency, in needs disbanded. 
I think some of the agents are honestly trying to do
a good job, like the original writer of the opinion that
allowed shouldering the Sig Brace.  Even an "SBR"
needing a tax stamp is ludicrous IMO... among
other things that they base their jobs on  :'(

HI PABLO!!!  <RGR goes back to reading thread>   ;D

In most countries in europe a suppressor is about as regulated as bubble gum.  It is a safety device in their mind.  As it should be in ours.

+1 on suppressors. Anyone have any info on the "Hearing Safety Act"?

Pablo, the firing pin will hopefully help.  Range Report soon?

I will not really look at a 10mm Carbine until there is a bigger Glock Mag available.
Do you know how the 1911 and Glock pistol conversions run?  I prolly have enough
toys for now, anyway   :P  Gotta pay some bills first, then more ammo  :))  :))

I will have a sweet 28 round HP 4595 if I get my butt into the shop!   

I googled variants of bent AR firing pin. Causes and such. I got nothing. Some yahoos bend the back end of the pin with the hammer (doh)....mine is bent up front.

The whole bent firing pin thing is new to me, Pablo !  I can see where it could happen but it seems to me that it would take a heavy strike from the hammer as well as a longer than normal firing pin to accomplish bending the pin.
  I have heard of guys shortening their firing pin slightly because it was long enough to cause primer perforations but I have no experience with this problem.  It would seem to me that your situation would call for a thorough inspection of the firing pin length, length of the bolt, depth of the well the firing pin runs in within the bolt, bolt face and length of the total unit when installed in the carrier. Common sense says that their can be variances in these measurements when the parts are machined. If you have enough variation in several of the parts it could lead to the total unit being out of spec enough to cause the bent pin and other problems.
  Since you have multiple AR's you shoul be able to get out the calipers and chart the variations you have in the parts you have available to measure.  You also might be able to get a diagram online which spells out the demensions and tolerances of the individual pieces.
   You would be looking for things that allow the pin to travel forward too much such as too deep a well in the bolt, or an accumulation of out of spec dimensions which lead to the same thing! I would also give the bolt face a good look.
  Also check out the hammer spring, you might need a less strong spring.
  Another spec to check out would be the "shelf" or ridge in the bolt carrier that prevents the firing pin from moving too far forward.

Let me start by saying WOW. I am having very similar issues w/ both of my QC10/RMW ARs, one in .45 & one in 10mm. It gives me hope that w/ this info you guys are sharing I may get them to run reliably. I have had slam fires;  I have had one of them go brrrup for 3 or 4 rounds; constant failure to feeds, failure to extract, failure to eject?; my mags seem "loose" in the magwell....yea problems. I oiled them up (like an Irishman goin to the beach),cleaned the bolts,  changed mags, changed ammo, changed shooters & even had friends who are Colt armors look them over & try to run them (aka a smart person unlike me) to no avail. I spoke w/ QC10 who gave me some ideas but no luck. I emailed RMW & well that did not go well "it ran for me"  :(
So they both sit in my safe waiting for rust or the gov't to take them away. (I live behind enemy lines in the republic of new jersey)
I'm going to try the ideas you folks have shared & maybe sacrifice a chicken to the gun-gods & see what happens.

This is my first post, my name is Don, I am as mechanically inclined as Ray Charles.  ;D

For awhile, I thought I was the only one. But people have emailed and PM'd me on various forums with RMW 10mm issues. I can understand why and it gets a little weird.

QuoteI emailed RMW & well that did not go well "it ran for me"

I like Ron and he has helped me, I even sent my upper and mags back to him. Same response - "it ran for me". I basically gave up contacting him, yet I believe he would still try to help if I asked. That said, he has certain avid followers on AR-15 and other forums, who jump down the throats of people who speak up and say they are having problems (rather than actually helping)

I have come to the conclusion he is not lying when he says it worked for him. But perhaps something is different about his full auto lower, different hold on the magazine, different forces on the hammer coming and going, different buffer and spring.

I know for a fact the BCG is cheap junk compared my better AR's. My bolt rings were trash, my carrier is very rough inside and my firing pin was bent. I would say start there. A DI 10mm and really a .45ACP need ALL the help they can get. the BCG should be super free moving. I never had slam fires or full auto (hmmm bent firing pin??) - just saying.  Took me a little bit, but my BCG feels perfect now.

I received my Militec yesterday. Oiled up and ready to try. Perhaps this late afternoon.

Hi Don,
  First of all, welcome aboard!  It great to have a forum where we builders of pistol caliber, DI operated AR's can compare notes and work the bugs out of our particular builds.
  I don't have any experience with the .45 AR, but some of the info I can contribute will probably apply regardless of caliber. The .45, of all the variants we all own, probably is the lowest pressure round with the largest bore and closest gas port and therefore is the hardest to make run properly.
  Of four of us who own these builds ( you, Pablo, SStewart and myself ) it appears that the two who are having the least problems ( SStewart and myself ) reload their ammo while you and Pablo appear to use off the shelf ammo of various brands.  I believe this is an important difference.
  Due to the fact that the gas ports on these weapons are located fairly close to the chamber, it is easy to see that a round that burns poorly creating a lot of carbon and crap is going to cause problems as that " junk" accumulates in the bolt area. Since pistol rounds in general operate at less pressure than the rifle rounds the system was originally designed for there is little opportunity for the gas and pressure to "self clean" by blowing excess build up out of the bolt. It seems that this build up is the cause of many of the problems you are experiencing, such as failures to feed and eject as well as slam fires.
  Also making your own ammo allows you to tailor it to the correct pressure curve and pressure to operate the action. This is important as too slow a build up in pressure will cause more unburned powder and debris to go into the gas port and slow down the action.
  Do you reload? If not, do you know anyone that does?  It seems that both SStewart and I reload and use the same powder ( Longshot ) and we are having the fewest problems by far. If you can't get reloaded ammo with Longshot, as I suggested to Pablo, you might contact Underwood ammo and see if they can provide you with a 180grain 10mm load powered by 9.6 grains or so of Longshot. Clean your weapon thoroughly, including scraping the tunnel in the bolt where the firing pin runs and see if the different ammo helps.
  You might try a healthy load of Longshot in .45 also. I'm not sure if Longshot works well in the .45 but it's worth a try. Again, Underwood may be able to supply .45 rounds also, I'm not sure.  Other clean burning powders might work in .45.  Also, using magnum primers may help by providing a quicker, cleaner burn.
  I have not had problems with carbon build up but have to admit that I generally clean mine after each heavy use.
   If you have read my post you know that my first QC10 lower had problems due to the fact that the magazine was too low in the magwell causing failures to feed. Quarter Circle 10 recognized the problem and exchanged my old lower with their newer one which holds the magazine in a higher, correct position. The difference was amazing and my failures to feed problems went away. You might contact them to see if you have an older lower and if so exchange it for the newer design.  They were great to me and exchanged the lower while paying for shipping both ways.
  The slam fire problems you are having has to be due to the accumulation of crap and carbon around the firing pin causing it to not move freely.  I keep mine fairly clean and have not had this problem. The Longshot powder appears to burn clean enough that I have not had serious carbon build ups to deal with.
  Pablo experienced a bent firing pin, probably due to carbon build up jamming the pin or a pin that was too long, so you might check yours to insure it is straight. Remember, there is no spring on an AR firing pin so it must fit loosely to prevent slam fires.
  I hope I have not bored you with this info as some of it is a re-cap. Try it out and let the board know how it works. I'm sure your problems can be overcome and a report on your experiences will help others!
 

Great post (again) mrpipesmkr. I think we were both typing at the same time.

My only difference (of opinion) - is I believe (no evidence either way) is the way my firing pin is  bent, it's always been like that. Junk BCG.

That said, definitely some very subtle length differences, geometry, are involved. My near term goal is one chunk at a time. Get my BCG perfect and keep it super clean. The Militec is being baked on in the shop right now at 140°F. When I get my morning work squared away, I will get my brass out, set my press up and get some Longshot rounds loaded and hit the range. My days are a bit variable AND due to construction, the range is closed during day working hours. (Opens at 4PM and gets dark at 4:30PM!!!)

I forgot to mention, I have loaded .45ACP with Longshot for my Camp Carbine and 1911's and SA XDS and other guns. It works, but it's not accurate at all until you go max book load. Which really isn't that hot, IMHO. So to get a .45ACP DI AR to run, you probably will have to go over book.

Hey Pablo,
  Yeah, we must have been online at the same time!  I live in the Dallas- Ft. Worth metro area and was up early due to a few things I had to get done. I did my post and left but did not see yours until later.  I believe you are on the West coast so you must have been up late!
   Glock10mm (Don) seemed pretty frustrated with his build and I wanted to respond to his post before I was out and about this morning.
  As far as the bent pin goes I just assumed it must have happened when you were firing the weapon but you know what they say about assuming things. Since you have the pin to look at and I don't you are in a better position to evaluate what caused the bend.
  From your post I assume you did find some different measurements in your various bolt groups. Are these enough to jam the pin and cause it to bend?
  The mil-tech sounds interesting. Let me know if it works in terms of lubrication and keeping the bolt and pin clean. I do get a build up of carbon on the tail of the bolt but never enough to affect function.
  All I have left of my .45's is a set of dies. When I went to the 10mm I had to sacrifice a few things to finance my new interest.  I wish I was rich instead of good looking!  Anyway, your info on .45' s and Longshot should be helpful.
   I have not talked wit Ron for more than a month but he has always been patient with me and has helped with several problems. He is pretty busy but he will take the time to try and help with a problem. He is the one who figured out that my QC10 lower was out of spec as well as other customers he had, and contacted QC10 to convince them they had a problem. My new lowers are much better.
   I will say that I do notice a difference in the smoothness of my RMW lowers when compared to my .556 AR. The .556 is smoother but I attribute this to the thousand of rounds put through it, it is well broken in.
   So far I am generally happy with Ron's work but do not deny that I have had a few bugs to work out.  I usually talk to him on the phone rather than email and I think I get better feedback this way.
   Let me know how your trip to the range with the Longshot loads goes. I hope the factory ammo is the problem because that is an easy fix!
   

I didn't get to do much gun stuff yesterday. Too much other stuff going on right now. Busy in a good way, but not enough long interludes to load ammo or go to the range.

Went shooting at 22°F this AM. Fingers hurt a little at first, but it was beautiful at the range. Plus, I was the only one there, until another guy showed up. To my pleasure it was DAVE WORKMAN!!

So the 10mm AR...... It only had one type of feeding failure. This is actually progress!!

I only used Sig and Underwood. 180gr. Used three labeled magazines.

Zero ejection failures.

The ONLY issue, about 1 in 8 rounds is a partial chambering stop. The round was angled and hung, mostly ready but lodged and not entering the chamber fully. I need to see where and how it's hanging up. Happened exactly the same with Sig and Underwood.

Took it down.

Hmmm.....wow the bolt is very gritty and tough to move. File for later.

Whitish powder puff debris all about. Not sure what to think about that. I shot 100 rounds, it's like one round didn't fully detonate. I've seen this white stuff in 357Sig, sometimes in .45ACP.

Cleaned it all up. A little grit on the bolt tail, but cleaned up nicely. Nothing remarkable.

So I took a round and with the upper alone (no BCG), dropped a round in. Hmmm, sorta hangs at the top were the case lip hits the upper chamber entrance edge. Hmm...a pretty hard stop. Thoughts?

Sounds like a 1911 style "three point" failure. I am not familiar with this gun, but in the 1911 that indicates a need to clean the extractor install up and/or install stronger mag springs.

Quote from: sqlbullet on January 01 2016 03:17:29 PM MST
Sounds like a 1911 style "three point" failure. I am not familiar with this gun, but in the 1911 that indicates a need to clean the extractor install up and/or install stronger mag springs.

I think different forces at work here. Extractor spotless.

Could be a mag issue.

If it was a .223 platform people would be talking about the feed ramp(s).

If the 10mm round entered the prechamber area at less of an angle it probably wouldn't jam....I think...

Pablo,
  Sounds like some progress was made! Much better day at the range than you've been having lately! Do you attribute the improvement to the new militec lube or the ammo?
  I'm about convinced to follow your lead and try the Miltec lube using the recommended heat application. Been running both my builds with over lubrication for break in but I think there bath there now. The over lube tends to help with the break in but does trap powder residue in the action. I'm thinking your Miltec, properly applied, with a very light coat of oil over it may run the gun cleaner, attract lest carbon, and therefore be more reliable. I shoot both my builds yesterday and had few problems with either, two or three partial feeds that required the assist.  Usually this was with a full or nearly full mag.
  Now to your problem, which I have experienced also.  Don't know if I can clearly explain how it was happening in my 9x25 but will try.
  If you recall, the first lower I got from QC10 was not engeneerd right and held the mag too low in the well. This created the exact problem you are reporting. I looked at it and talked with Ron on the phone and he explained that with the mag so low the lugs on the bolt were only able to make partial contact on the round and this contact was only on the upper rim of the round. This partial contact in effect allowed the round to "flop" up and down, pushed by the mag spring as it went forward. So many times the round would hang up as it entered the chamber on the upper edge. The answer was to find a way to raise the round so more of the two bolt lugs would make contact with the round.  The lugs should contact the round further down near, or on both sides of the primer. This tends to keep the nose of the round pointing at the chamber.
  What I did on the old lower was alter the mag lips to raise the round higher in the mag to allow better contact. Because I could only raise the round so much without making the mag unable to hold the round this was only partially successful but did make a drastic improvement.
  My feeling, since your pretty close and only having a few miss feeds, is that raising the round will solve most of your problem, if not all. (Remember I cannot see your problem, only visualize it, so may be way of base). I would slowly close the bolt on a round and see where the lugs are contacting. If it's high on the round it is definitely at least contributing to your problem.
  If you've already spread the lips as far as possible and still hold the rounds in the mag then you need to find a way to extend the lips. I had thought of finding a small metal tube, similar to a ball point pen cartridge, slicing it down one side, slipping one of these over each of the lips and soldering them in place using silver solder if necessary. There may be other ways but that was all I could think of.
  I did also have some success by altering the slot where the mag catch rests in the mag. By cutting away some materiel on the lower part of the slot the mag would fit higher in the well. I had to add materiel on the upper part of the slot to keep the mag from slipping down in use.
  Anyway, my problem was solved when QC10 exchanged my old lower for the new one which held the mag and consequently the round higher. 

QuoteDo you attribute the improvement to the new militec lube or the ammo?

Neither directly, although I think the Militec helps.

The improvement came from freeing up the bolt:

1) Honing and removing all burrs in the BC - the "cylinder" was very rough and nasty- I used metal polish and the old rings on the bolt. Made it very smooth. Suggested in this thread.
2) Replacing the gas rings with a one piece ring - JP Enterprises - these are still taking a seat, but seem to be making a better seal, hence better action. My idea.
3) Replacement of bent firing pin - this pin was consuming extra energy and was not right. Replacement pin is still straight. Should have been straight from the start (arrgh!)
4) Use of a Tubbs flatwire pistol caliber carbine spring - less resistance to gas pressure, of course less spring force on return, but now the trigger sets reliably. My idea, and used by .300 Blackout guys.


So basically I changed lots of things outside the chamber, and didn't have a:

A) Failure to eject - all spent cases appeared to fly out at 80°-120° from the rifle, most about 110°.
B) Double feed
C) Stove pipe
D) Failure to feed that didn't set the trigger

Not yet saying these things are eliminated, but simply didn't happen in 100 rounds of both Sig and Underwood 180gr FN (Now I should mention the Underwood felt significantly hotter FWIW)

The feed issue could very well be the magazines. Since I have no pictures or actual dimensions of what a proper adapted grease gun magazine should look like or measure, I am flying a bit blind here. The mag Ron sent is not perfect, so that really doesn't help.

Again - positive progress. Thanks!

Edited to add details

Pablo,
  I guess I'm one of those old guys who is tech challenged! I had already responded to your post earlier and was editing it to clear some stuff up when I managed to wipe out the entire post! Sorry if you had already read it and I created confusion.
  I'll try to recap the post.
  I think I will get some of the Miltec and apply it with heat. I have been overlubing  fo break in but think both my builds are pretty much there. The Miltec treatment with a wipe down of light oil over it should allow the gun to run cleaner as it will trap less residue and allow the pressure to blow more residue out.
  The only consistent problem I have is an occasional partial feed requiring the forward assist. This usually happens with a new, tight mag , but also may be due to the chamber being tight. I am considering taking a wooden dowel and 600 grit paper to loosen it up a little.
   I used the white turtle wax early on with my piece to speed break in. I used it on the rings, the four rails the bolt carrier runs on in the receiver and the face of the hammer. Seems to me with these PCC's you are fighting for the most efficient use of the available gas pressure and anything you can do to eliminate friction and drag is a bonus.
  I still feel that reloading with Longshot will help your piece, clean and a good pressure curve.
  I can't emphasize enough that you should verify where the lugs on your bolt are contacting the round to strip it from the mag.  I became very familiar with this problem due to my old lower being out of spec.
  Put a couple of rounds in your magazine. Hold the bolt back manually with the charging handle. Insert the mag in the well and slowley allow the bolt to move forward. Observe where the lugs are contacting the round. If they are only contacting the upper portion of the rim it is contributing to your problem. The only thing you can do about it is figure out a way to raise the mag in the well to achieve better contact on the round.
  Sorry for the confusion with my first post but hope this helps!

Yeah I thought I was losing it!

I actually get email notifications, so here is what you typed:

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The text of the reply is shown below:
Pablo,
  Wow, what an improvement! I'm happy to see your build come around to where it's at and hope the final kinks can be worked out.
  Freeing up the bolt group is something I did early on and seemed to help. That's why I suggested the white turtle wax polish for your rings.  I also used the same stuff on the four rails the bolt runs on in the receiver and the face of the hammer just to smooth them out. I for sure didn't over do it and maybe could have done more but I think it sped up the break in.  Break in is very important, it seems to me, on these PCC's because you are fighting for efficient use of available pressure.
  I still feel that doing your own loads with the Longshot powder will help overall.
  The only consistent problem I have now is occasional partial feeds that require forward assist. My chamber is fairly tight, which I like because it helps build pressure quicker and is easy on brass, but I may have to take a wooden dowel and some 600 grit paper and loosen it up a little. The tight chamber may be contributing to my occasional partial feeds, although tite, new mags seem to contribute also. Because I need good forward speed on the bolt carrier I have stuck with the standard recoil spring rather than something like your running.
  I can't emphasize enough to examine closely where the bolt lugs are catching the round as it sits in the mag.  Due to my old lower being out of spec I became very familiar with this problem!  Put a round or two in your mag, manually hold the bolt back with the charging handle, insert the mag in the well and very slowly let the bolt go forward. Observe where the lugs contact the round to strip it from the mag. If it is hitting only the upper portion of the rim this is contributing to your problem! I fought this same feed problem with mine. The only solution is to figure out a way to raise the mag in the well for better contact between the bolt lugs and the round.
  Anyway, I feel like you "over the hump" on you build and on your way to a trouble free shooter!  Congratulations !

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Pablo,
  Glad you got and managed to save the post. Don't know how I managed to delete it!  Give me a car and I can take it apart. Give me a gun and I can figure it out.  Computers I can turn on and off, search a little and type, that's about it, and pretty slow at that! Generational thing, I think😁  Sometimes my daughter has to rescue me from my computer😳
  Anyway, hope our exchanges have helped you and anybody else following them.  They have provided me with new ideas and helped improve my builds!
  Keep us posted on your progress on your next range trip.

So in the meantime I was working on other things. But I did try the slow feed per your suggestion.

It seems the slow feeding doesn't work at all, the bolt face or front surface of the lugs just kick the cartridge up so I get a different style of fail to feed jam. This type is nose down stop. Just drop the bolt hard and it feeds fine.

It's good to observe the bolt and top of feedlips relationship though. I cannot imagine the magazine any higher up. The specially machined BC base just rides the feedlips. In fact IF I rest the rifle on the magazine (ie forcing the magazine up), it collides with the BC.

So back to the magazines. I have to tell you, I have four GG magazines and they are all the same as far as construction, and even the machined (by RMW) mag catch slot are all the same. That said the feedlips are all different. (One is a bit mangled up with my ham fisted approach, so I set it aside. ) That said all mags seem to behave the same at the range.

Next range trip, I will take the one with the largest front spread, open it a bit more, make no other changes and see what happens compared to the other two.

Pablo,
  Sound like your covered on the mag hight.  I was sure my experience with the low mag was related to your missfeeds but maybe not. Again not being able to actually see your action I have to visualize what's going on and can get it wrong.
  I did not think your piece would slow feed as they all need some velocity on the bolt and carrier to feed properly. I was just wondering where the bolt lugs initially contacted the round. With my old lower raising the round so the point of contact was lower on the head of the round made a significant difference.
  Apparently where your mag sits now you nearly have contact with the bolt lugs on the mag lips.  I had the same close tolerance with the Glock mags initially and I'm sure during firing the weapon was sometimes getting contact at those points. This slamming the mag around was contributing to the missfeeds I experienced.  To alleviate that I took a Dremel and stone and shaved the two feeding lugs on my bolt thinner, taking the material off the sides of the lugs that were contacting the mag lips. This extra clearance made a big difference. I left plenty of metal on the lugs to strip the round and lock the bolt closed but created as much clearence as I could.  If your two lugs are not ground a little thinner you can improve the clearance by taking a little metal off.

Good stuff.

I just told myself: Step back for a moment. Breathe. Think.

So, say a problem happens every 8-10-12 rounds. On one hand, HUGE problem. Of course. On the other hand, some issue that doesn't happen every round or every third round, could be pretty subtle.

Pablo,
  Here are the pics of the shaved lugs on my bolts. Pics aren't the best but maybe you can see what I did. I did the grinding on the 9x25 and Ron did the 10mm.
  As I hope you can see, I did not shorten the lugs at all, just narrowed them down from the side that was contacting the mag to provide more clearance.   You want to leave them long so they make contact as low as possible on the round.  We left them wide at the base and narrowed them down more at the tip to maintain strength and achieve the most clearance.
  If you are having any contact of the lugs and your mag this will help solve the problem.
  If you have any questions post or PM me.

[attachment deleted by admin]

My lug is definitely not cut like that. Interesting.

Pablo,
  The AR15 was designed to feed from both sides of the original magazine. When we change over to Glock mags and I assume, GG mags, the weapon has to feed from the center of the mag. The lips of the .556 mags are much farther apart because they hold two rounds, side by side. The single feed mags, such as Glock, have the lips much closer because they only hold a single round. To feed from the single the bolt carrier has to be narrowed so it will fit through the lips of the mag.  But, these narrow single feed mags also cramp the feed lugs on the bolt, sometimes causing contact between the lugs and the lips. If this is happening, that contact can cause the round to missfeed. By grinding the appropriate sides of the bolt lugs you are providing more clearance between the lips and the lugs, eliminating the problem.
   Here, I have to add that I am not real familiar with thr GG mags. Don't know what kind of clearances you have, but take a look and see. If they single feed chances are the clearances are close.

This is a full work week for me. I need to study my rifle vs. what you are saying, just don't have time right now.

I didn't have any dummy rounds made up (easy I know) - but I scored some 10mm dummy rounds locally for low $. I was becoming uncomfortable chambering a live round! I'll see how they behaved and I will watch the bolt over the mag.

Pablo,
  I know what you mean about chambering live rounds! I get queasy every time I have to do it!
  No problem if you are busy at work! We gotta make money somewhere to pay for our expensive toys! I just wasn't sure if I was making sense or not, trying to describe the work we did to the lugs on my builds and I wanted to be sure my meaning got through. I hope the pics made more sense than my verbal description. I know it was something that helped my builds and hopefully could help yours.
  Again, you have to be the judge as I have next to zero experience with the GG mags but if they feed from the center then it needs to be looked at!
  Did you decide on the 9x25?

I won't get the 9X25 barrel until this one is running perfectly. Thanks!

Does make me wonder if the shouldered 9x25 would feed easier and my problem would be cured. I did receive my titanium firing pins last night. Wow they feel light.

I have a di qc10  10mm ar that im trying to get the bugs out of as well my issue is the bolt doesn't close all the  way on the first 7-9 rounds and I have to eject the mag and slam the bolt shut till I get to about 5-6 rounds left then the weapon cycles fine I already have the updated lower receiver that helped a bunch any tips from you guys

Sounds a bit like you have a sticky bolt. I would do the stuff I mention to free up the bolt in the carrier and get a flat wire spring. None of these things will hurt and most likely will help. It is a bit odd that it improves as you shoot it for that session only . Are you starting with a clean gun? What lube? Outside temp?

Quote from: sgmtino on January 06 2016 01:35:36 PM MST
I have a di qc10  10mm ar that im trying to get the bugs out of as well my issue is the bolt doesn't close all the  way on the first 7-9 rounds and I have to eject the mag and slam the bolt shut till I get to about 5-6 rounds left then the weapon cycles fine I already have the updated lower receiver that helped a bunch any tips from you guys

Sgmtino,
  First of all, welcome aboard!  Always good to have another 10mm DI AR owner to contribute their experience to the board.  I think the idea here is that by pooling our knowledge and fixes we all can end up with reliable 10mm and 9x25 builds. A couple of us have builds that are running pretty good.  The 10mm in a carbine or SBR is just a whole lot of fun.
   Can you give us more info on your build?  Who did the upper, barrel length, Glock mag or other (QC does build other lowers) ect. This will help to compare yours to others.
   The first thing I would say to you is take the time to read all the posts on this board and see if any of the info and fixes can be applied to your build. There is a lot of info posted by the various members dialing in there builds and some of it will be useful.
I think I have experienced the type of problem you are dealing with and have, for the most part, cleared it up. I still have an occasional partial feeds with new mags but they are fewer than before. In my case the round was feeding straight into the chamber but stopped before the bolt fully locked. I usually just have to tap the forward assist to close the bolt.
  I think what was going on with mine was simply that the bolt carrier was not returning with enough force to close the bolt. I think this is because these builds tend to be quite tight when new, before break in. The 10mm does not have the gas pressure of say, a .556 so the carrier may not be moving all the way to the rear of the buffer tube and therefore does not close with enough force.
  As Pablo suggested I went in and used polishing compound to "loosen up" my bolt and smooth out the rings and bore that they run in. This takes some repetition but does take the stiffness out of the bolt. Pablo has also gone to the one piece ring and feels this was an improvement, I have not, yet.
Because these builds tend to be stiff due to the coating used on all parts I also decided to help break in my build by polishing some of the wear points in the upper and lower.
  I used a Dremel with felt pad and polishing compound to smooth out and remove the coating to cut down on friction and drag. You don't have to polish to a high shine on these wear areas but you do want to polish until they are smooth. Polish all four of the rails the bolt carrier runs on, the bolt and rings (as stated) the retainer pin, the tail of the bolt, the face of the hammer and the portion of the carrier the hammer runs against.
  This should help minimize the drag and improve the speed of the carrier as it moves forward.
  Also check to see if the bolt lugs or carrier is rubbing against any part of the mag causing a slow down.
  I have also ordered some of the Militec lube. I think if it is applied properly, according to instructions, it will help reduce drag.
  Let us know how it goes and we will all work together to perfect our builds. All in all, they are a ton of fun!

Quote from: Pablo on January 06 2016 01:28:17 PM MST
Does make me wonder if the shouldered 9x25 would feed easier and my problem would be cured. I did receive my titanium firing pins last night. Wow they feel light.

Pablo,
  My experience is that the 9x25 does feed easier than the 10. Smaller bullet going in to a large chamber.  Less rubbing, less drag.
  The Titanium pins sound interesting, let us know how they work.

You had me at titanium.

It appears as if the Ti firing pin will work fine.

So I loaded up a magazine with 10 dummy rounds. I could really see how they chambered - first of all they chambered perfectly with released bolt catch, bam. That is as expected. Seems like this magazine is tuned correctly.

Then I restuffed the magazine and went slowly....

a) Bolt contacts round
b) Bolt pushes round
c) it looks like bolt slightly contacts mag lips
d) round actually releases and pops up
e) bolt pushes round in chamber (now in slow-mo) the round will hang sometimes, but will chamber with assist button.

My problem may be as simple as the design of the 10mm cartridge with the necessary case edge hitting and catching the AR chamber entrance.

The big difference between the dummy rounds and the rounds I have been shooting is the case crimp area. The dummy rounds is not pronounced at all while most all ammo types I have the lip is quite sharp.

Pablo,
  I believe the titanium pin should be stronger than standard, no more bent pins!
  It s hard for me to say what your problem with feeding is without watching the action work. I believe the lugs contacting the mag lips is not a good thing if occasionally it causes a jolt to the mag which throws off feeding, but it sounds like there is no major contact between the lugs and the lips.
  If the round is going nose up as it exits the magazine causing a missfeed you might check and see if the front of the round or the case lip is contacting the front of the mag, throwing the nose up. If it appears this is happening, taking a little metal off the front of the mag would give better clearence.
  When the lugs contact the round are they hitting it low, below the rim, somewhere near the center of the case head? This would tend to make the round go straighter into the chamber.
  Anyway, it sounds as if most of the bugs are being worked out of your build! Let us know how your next range trip goes!

I will now further examine the relationship between the lower bolt lugs and the magazine.

Quote from: Pablo on January 07 2016 01:26:28 PM MST
I will now further examine the relationship between the lower bolt lugs and the magazine.

I believe polishing those two bolt lugs is nearly miraculous. The next round does not appear to be irritated in the least by the bolt traveling headed back. The lugs just glide over.

But allow me to summarize the most recent changes:

I'm still perfecting this 10mm, but the steps I have taken, have made it a lot better.

1) Oddly the firing pin was ever so slightly bent/out of round, cheap thing. Replaced with a titanium pin. Probably not a huge deal, but was slow in the bolt.
2) Bolt was nasty rough in the carrier. Honed with the stock rings and alloy burrs and carbon broke free, replaced rings with JP Enterprises one piece.
3) Polished the cam and associated parts.
4) Lubricated with Militec
5) Kept same buffer weight (tried a heavy buffer, with original and rifle would barely cycle if at all)
6) Replaced spring with David Tubb's pistol carbine flatwire spring (this probably has made the largest difference outside the BCG)
7) Buffed the bottom two bolt lugs to a mirror finish, after breaking the trailing and inside edges.
8) Replaced the extractor spring with a HD spring and core but no o-ring
9) Super buffed the extractor face and removed all the burrs and super sharp edges that tore up brass rims
10) Deburred and buffed the cam way and cam pin.

All these things made the rifle run a LOT better.  In fact you wouldn't believe how smooth the action is now since working over the bolt and carrier. I never felt any stock AR BCG this smooth and my very first AR is a Daniel Defense which now has around 12,000 rounds through it and is still not this smooth. Cleaning the bolt up makes that much difference, and is a must do on a 10mm AR.

Took it to the range yesterday.

The gas system ran exceptionally well.

The only hang ups I had were case rim at the chamber entrance. I need to figure out if it's feeding issue or the chamber entrance is too tight. I contacted Ron earlier on this earlier and he suggested opening the chamber up.

Very happy for you !! ;D
You have worked very hard to get these results.
I'll have to look at doing some (or all) of the things you have done on mine.

Over the past five weeks or so Pablo and I have been in close communication discussing our 10mm and 9x25 carbine builds from RMW extreme.  By explaining to each other improvements we had done to our builds and future plans to improve them we set up a situation where we brainstormed our way into making our carbines run very reliably.  They can be made to be very reliable, and when you reach that point they are a lot of fun to own and shoot.
  This excersize has proven to be a lot of fun for both of us and a learning experiance that is hard to match in terms of pistol caliber DI AR's.   But, we don't believe that every owner of an RMW extreme build would want to go through the many ideas and changes we have had for our builds.
  Our hope has always been to distill what we have done to our builds down to an easy to follow list of important improvements that others could use to improve thier builds.
  So, the following is a distilled list of things we have done. The list is in no particular order but is fairly comprehensive. We will add any other improvements we might have done should we recall them at a future date.

1)    installed Tubbs flat wound spring, Pistol and 300Blackout model.
2)    installed H2 buffer, weight 4.4 ounces
3)    made sure the buffer and spring were lubed
4)    used both the JP and standard rings, depending on build, well broken in
5)    Polished the bolt face until it shined, making sure any ridges were well rounded
6)     polished the cam pin, rails the carrier runs on, hammer face and the ramp the               
        Hammer runs against.
7)     used 600 and 800!grit paper to smooth the chamber walls
8)      polished the chamber walls including the cone at the start of the chamber
9)      polished the firing pin
10)    Trimmed, rounded and polished the bottom two feeding lugs on the bolt insuring that enough material
         was removed to insure the lugs cleared the magazine. Smooth polish eliminates drag on the
         next round feeding in the magazine


    Both Pablo and I will try to answer any questions you might have. The important thing to remember is that with a little tune up work you can have a very reliable carbine that is tremendous fun to shoot.
   It is important to remember that Pablo's build and my two builds are a little different.  Pablo's build is based on a lower that uses GG magazines. My builds both use the QC10 lower and run Glock magazines.  Still, the work we did on our pieces was very similar with a few small variations.

If you look at my list above. And pipesmoker's more comprehensive list there is one thing that stands clear. A 10mm gas AR starts life fundamentally undergassed. Really almost all efforts need to start with this concept in mind, and the corny goal motto could be: If I can set my 10mm AR up to run on puny factory mouse rounds, it should be a very reliable rifle with hot slow burning powder rounds. Because frankly Ron at RMW does not at all set the BCG and springs up run with anything but the hottest home loaded ammo.

So the number one thing to take from these lists is make sure ALL moving parts are finely polished and move like a Swiss watch. Not only did I learn a lot about the AR-15 platform, I really came to appreciate just how smooth the AR can be, and how nice you can make ALL your AR's. You can get your magazines feeding nicely, your chamber feeding perfectly - but if your BCG is not freely moving, your rifle won't run.

Yes, we both feel qualified to help and guide. I have now had a couple+ people contact me. Either wanting to buy, questioning my motives, previous or current RMW owners. I too had my doubts at some points if this would even be viable. Others have given up. Ron has sent refunds. That can't be good for him. We want to succeed. We want others to succeed and we want Ron to have a successful business, despite what some people on arf.com accused me of (like this whole thing was junk I made up!).

So ask us. Start a new thread. PM us (we prefer public so all can gain) . Communication is good and love for 10mm Firearms.com is best!

Sorry to be that guy, but I don't wanna dig back through the 10 pages.

You went to an H2 buffer.  What weight buffer did you start with?

I am a relative AR-noob, with only 2 completed builds (5.56 SPR and 300 BLK Carbine), and four in progress (CMP Service Rifle, 5.56 Carbine, 308 Win and 358 Win), and two yet to be started (260 Remington and an undecided 6.5mm in an AR-15).

It seems to me that an undergassed gun would want as little reciprocating mass as possible, aka a carbine buffer.  And possibly a JP Rifles low mass bolt carrier.  I have been reading the thread as you went and I don't recall these being discussed, but I may have missed it.

You I am curious of the H2 was chosen for additional momentum for feeding, and the gun was well enough gassed to drive it with a light-ish spring, or if I just am missing something.

Quote from: sqlbullet on February 12 2016 09:15:55 AM MST
Sorry to be that guy, but I don't wanna dig back through the 10 pages.

You went to an H2 buffer.  What weight buffer did you start with?

I am a relative AR-noob, with only 2 completed builds (5.56 SPR and 300 BLK Carbine), and four in progress (CMP Service Rifle, 5.56 Carbine, 308 Win and 358 Win), and two yet to be started (260 Remington and an undecided 6.5mm in an AR-15).

It seems to me that an undergassed gun would want as little reciprocating mass as possible, aka a carbine buffer.  And possibly a JP Rifles low mass bolt carrier.  I have been reading the thread as you went and I don't recall these being discussed, but I may have missed it.

You I am curious of the H2 was chosen for additional momentum for feeding, and the gun was well enough gassed to drive it with a light-ish spring, or if I just am missing something.

YOU are exactly correct. I did not change my buffer, and in fact I bought the AIM low mass BCG (not modified and installed though) . I have the regular buffer and took out some mass out, but it didn't help all that much. A couple things going on here. First of all pipesmoker did use the H2, but he runs hot ammo, and as far as I know hasn't run lighter loads. PLUS more importantly all AR's need that dynamic mass in the buffer, so a lighter easier moving bolt is good, the impact smack is still needed. Mr Pipesmoker needs to now try a regular buffer with his cleaned up chamber and maybe try some factory dumb 10mm ammo.

Quote from: sqlbullet on February 12 2016 09:15:55 AM MST
Sorry to be that guy, but I don't wanna dig back through the 10 pages.

You went to an H2 buffer.  What weight buffer did you start with?

I am a relative AR-noob, with only 2 completed builds (5.56 SPR and 300 BLK Carbine), and four in progress (CMP Service Rifle, 5.56 Carbine, 308 Win and 358 Win), and two yet to be started (260 Remington and an undecided 6.5mm in an AR-15).

It seems to me that an undergassed gun would want as little reciprocating mass as possible, aka a carbine buffer.  And possibly a JP Rifles low mass bolt carrier.  I have been reading the thread as you went and I don't recall these being discussed, but I may have missed it.

You I am curious of the H2 was chosen for additional momentum for feeding, and the gun was well enough gassed to drive it with a light-ish spring, or if I just am missing something.

Sqlbullet,
  No problem, I wouldn't want to read through 10 pages of old posts either! That's why Pablo and I decide to post our list on the board.  We will help all we can and try to clarify anything that seems confusing.
   I originally used a standard carbine buffer (app. 3 ounces) in my builds.
   Installed the H2 buffer in both my builds. You are right about the reciprocating mass and weight. I found that increasing the buffer weight (4.4 ounces) helped my builds to feed easier. I was having trouble getting proper feed out of my Glock mags when they were full.  Adding the mass seemed to help and both builds have enough gas to run the buffers. Pablo is right that I run somewhat hot loads. My standard is a 180 grain Hornady HAP pushed by 9.6 grains of Longshot with a standard primer. I have run other loads such as 155 gr with equal success.  Lighter bullets use more powder which in turn creates more gas volume and pressure.
  The Tubbs flat wound pistol and 300 blackout spring was a big help with this. It ran somewhat with the standard carbine spring and not at all with the Wolf extra power spring.
  The Tubbs spring is designed to exert equal force throughout its travel where the standard spring creates increasing force as it stacks up. This means the pressure created by theTubbs when the bolt is closed on a round is greater, requiring more pressure to move it, increasing lock up time and the available pressure to move the bolt and carrier.  As the bolt and carrier move back they encounter less resistance from the Tubbs spring than they would with the standard spring when it begins to stack. Therefore you don't lose much if any velocity on the bolt and carrier.
  It's important to point out here that my 9x25 build has an adjustable gas block on it which I can use to help tune it to the H2. I put the H2 in the 10mm, got it to run, liked it, and then put it in the 9x25 with a slight adjustment to the gas block.  The adjustable gas block cannot be installed on the 10mm because there is not enough room in the gas system for it and besides it needs ALL available gas.
  I hope this info helps clarify!

Before we do a better consolidation, feeding an AR with a case mouth spacing untapered round can be problematic as well. If the ammo has zero crimp, the gun will choke. Generally a mild crimp will be fine if every area from the magazine to the chamber is deburred and polished.

Quote from: Pablo on February 12 2016 01:12:22 PM MST
Before we do a better consolidation, feeding an AR with a case mouth spacing untapered round can be problematic as well. If the ammo has zero crimp, the gun will choke. Generally a mild crimp will be fine if every area from the magazine to the chamber is deburred and polished.

Pablo is dead right on this.  I hadn't really noticed the lack of crimp on the factory rounds I have bought. After talking with Pablo I checked out the crimp on some Armscore rounds I had purchased on sale. No real crimp on them at all! Just the bell removed and that's it.
  If you look at a10mm round you can see why this creates a problem. The case mouth on the 10mm is always very far up the bullet, just at the point the ogive is ending. This is the perfect position for the rim to hang up on anything and everything, which it does. Check your rounds out and crimp them if they need it!  It doesn't need to be an exceptionally tight crimp, but it must roll the rim into the bullet at least slightly. It will still headspace properly with a good roll crimp.

Thanks for the feedback.

At some point I wanna build a DI 10mm upper, but it is down the road.

Short term this is relevant to me on my 358 Win build.  I want to see how light I can do it.  Based on mfg. information, I think I can end up under 7lbs on an AR-10 with iron sights.  But, there are two big parts of getting there and one is a JP Rifles low mass BCG for DPMS pattern AR-10.  That bolt is used in conjuction with an adjustable FSB, and probably a Springco Orange spring.  The idea is to use the light bolt, buffer, dial back the gas to get full bolt travel without battering and then let the extra power spring provide the umph to get the next round fed.

I have a good head start in weight using the new TN Arms polymer AR-10 lower, which only weighs 6.8 oz.  And I tracked down a 16" medium contour 358 barrel from KAK.  I may pay to have it re-contoured to more of pencil profile if I just can't get the JP low mass to run.  The idea would be to shave 3-4 oz from the barrel contour to add back into the buffer and BCG.

Cutting to the chase, I am keenly interested in properly understanding the results of changing reciprocating mass components.  I would love to end up with a guide sized gun with 25 rounds of 358 Win on tap as fast as you can squeeze the trigger.  LPK gets here next Thursday.  Handguard is on backorder and that wicked expensive JP BCG has to wait for my 2015 bonus to be paid, probably in March.

Well. Now I am riveted.  ;D

Quote from: sqlbullet on February 12 2016 04:33:39 PM MST
Thanks for the feedback.

At some point I wanna build a DI 10mm upper, but it is down the road.

Short term this is relevant to me on my 358 Win build.  I want to see how light I can do it.  Based on mfg. information, I think I can end up under 7lbs on an AR-10 with iron sights.  But, there are two big parts of getting there and one is a JP Rifles low mass BCG for DPMS pattern AR-10.  That bolt is used in conjuction with an adjustable FSB, and probably a Springco Orange spring.  The idea is to use the light bolt, buffer, dial back the gas to get full bolt travel without battering and then let the extra power spring provide the umph to get the next round fed.

I have a good head start in weight using the new TN Arms polymer AR-10 lower, which only weighs 6.8 oz.  And I tracked down a 16" medium contour 358 barrel from KAK.  I may pay to have it re-contoured to more of pencil profile if I just can't get the JP low mass to run.  The idea would be to shave 3-4 oz from the barrel contour to add back into the buffer and BCG.

Cutting to the chase, I am keenly interested in properly understanding the results of changing reciprocating mass components.  I would love to end up with a guide sized gun with 25 rounds of 358 Win on tap as fast as you can squeeze the trigger.  LPK gets here next Thursday.  Handguard is on backorder and that wicked expensive JP BCG has to wait for my 2015 bonus to be paid, probably in March.

Sqlbullet,
  I've got to say, you are a very ambitious guy to come up with the idea for a rifle like the one you describe!  I carried an M16 around in the military along with some heavier stuff and can appreciate your desire to knock every ounce possible off your build.  It can be done I think, but you are going to have to do a very precise balancing act with your components to make it run. You'll end up with a pile of spare AR parts that were tried but did not work. That's not really s bad thing as you seem to have several other AR's to keep running also.
   I was thinking about your build and my response to your question regarding the H2 buffer and spring.  Weight wise, the H2 is out for your build unless you just have to have the added mass to get your weapon to cycle. 
   However, I wanted to suggest to you that it might be worthwhile to look into the Tubbs flat springs for your build, either the carbine or rifle spring, depending on your build.
   The way the Tubbs springs exert more power with the bolt closed and the way they smoothly stack in recoil would, I believe help your build to be more reliable without adding much, if any, weight.
   Just a thought on my part but check them out.  I really like the way they run in my builds.

This one should work: http://www.davidtubb.com/tubb-springs/bufferspring-sr-ar10

I'm thinking a 358 Win will have plenty of gas.

Thanks!

I will add it to the list in place of the sprinco orange.  Or maybe in addition.  $30 on this build won't break the bank.

I also came across this the other day:

http://www.vertexops.com/V_Seven_308_AR10_DPMS_SR25_Titanium_BCG_p/v7-bcg-ti-ar10.htm

Same price within a few bucks as the JP low mass, so I am gonna grab one when they are back in stock.

Once I get to the actual build part I will post up a thread on how it goes. Appreciate the input guys!

WOW that is nice. But expensive!! Titanium is light and strong, but are the thermal properties OK? Probably.

Doesn't  look like AIM makes a lightweight .308 BCG. Darn.

http://www.aimsurplus.com/catalog.aspx?groupid=2535&name=Bolts+%26+Bolt+Carrier+Groups

Why do you need a super light BCG? Are those undergassed? I'm confused, I guess.

Quote from: sqlbullet on February 14 2016 06:00:13 PM MST
Thanks!

I will add it to the list in place of the sprinco orange.  Or maybe in addition.  $30 on this build won't break the bank.

I also came across this the other day:

http://www.vertexops.com/V_Seven_308_AR10_DPMS_SR25_Titanium_BCG_p/v7-bcg-ti-ar10.htm

Same price within a few bucks as the JP low mass, so I am gonna grab one when they are back in stock.

Once I get to the actual build part I will post up a thread on how it goes. Appreciate the input guys!

I've got to echo Pablo.  WOW!!  Looks like quality stuff though.   How hard does the .358 feed?  Is it possible to have too light a weight in the BCG?  I suppose a heavier spring or buffer could be used if the BCG is a little light, and still represent a weight savings.
  Don't make book on it, but I believe the thermal properties of titanium are similar to aluminum.

It is nowhere near aluminum, which has great thermal conductivity.  It runs about 25% behind carbon steel, but this won't be a gun that I do mag dumps from. 

With regard to why.  Typically a "light" ar-10 will be 8-9 lbs before optics.  My goal is under 7 lbs to get it competing with a bolt action guide gun.  This BCG will save me 7 oz, nearly half a lb.  I will have to use an adjustable gas block to keep the gun from being ferociously over-gassed, and then ensure I have enough spring to feed a new round.

And it may not work at all.  In which case I will have a very expensive titanium bolt that either sits on the shelf, or that has an insanely heavy buffer behind it. :-\

But, I think I can tune it in just fine.  Lots of guys are making various low-mass BCG's run, so I figure I can find the magic combination.  And if it works like I think it will, I will have a light recoil gun in a heavy hitter cartridge that weighs 8lbs with a full load of 25 rounds.

Quote from: sqlbullet on February 15 2016 09:30:12 AM MST
It is nowhere near aluminum, which has great thermal conductivity.  It runs about 25% behind carbon steel, but this won't be a gun that I do mag dumps from. 

With regard to why.  Typically a "light" ar-10 will be 8-9 lbs before optics.  My goal is under 7 lbs to get it competing with a bolt action guide gun.  This BCG will save me 7 oz, nearly half a lb.  I will have to use an adjustable gas block to keep the gun from being ferociously over-gassed, and then ensure I have enough spring to feed a new round.

And it may not work at all.  In which case I will have a very expensive titanium bolt that either sits on the shelf, or that has an insanely heavy buffer behind it. :-\

But, I think I can tune it in just fine.  Lots of guys are making various low-mass BCG's run, so I figure I can find the magic combination.  And if it works like I think it will, I will have a light recoil gun in a heavy hitter cartridge that weighs 8lbs with a full load of 25 rounds.

Yes. I know about Ti. We use Ti spacers when we want lightness, strength and LESS thermal transfer.

Your answer makes perfect sense and that is a huge about of mass, gone.

Quote from: mrpipesmkr on February 12 2016 08:31:03 AM MST
Over the past five weeks or so Pablo and I have been in close communication discussing our 10mm and 9x25 carbine builds from RMW extreme.  By explaining to each other improvements we had done to our builds and future plans to improve them we set up a situation where we brainstormed our way into making our carbines run very reliably.  They can be made to be very reliable, and when you reach that point they are a lot of fun to own and shoot.
  This excersize has proven to be a lot of fun for both of us and a learning experiance that is hard to match in terms of pistol caliber DI AR's.   But, we don't believe that every owner of an RMW extreme build would want to go through the many ideas and changes we have had for our builds.
  Our hope has always been to distill what we have done to our builds down to an easy to follow list of important improvements that others could use to improve thier builds.
  So, the following is a distilled list of things we have done. The list is in no particular order but is fairly comprehensive. We will add any other improvements we might have done should we recall them at a future date.

1)    installed Tubbs flat wound spring, Pistol and 300Blackout model.
2)    installed H2 buffer, weight 4.4 ounces
3)    made sure the buffer and spring were lubed
4)    used both the JP and standard rings, depending on build, well broken in
5)    Polished the bolt face until it shined, making sure any ridges were well rounded
6)     polished the cam pin, rails the carrier runs on, hammer face and the ramp the               
        Hammer runs against.
7)     used 600 and 800!grit paper to smooth the chamber walls
8)      polished the chamber walls including the cone at the start of the chamber
9)      polished the firing pin
10)    Trimmed, rounded and polished the bottom two feeding lugs on the bolt insuring that enough material
         was removed to insure the lugs cleared the magazine. Smooth polish eliminates drag on the
         next round feeding in the magazine


    Both Pablo and I will try to answer any questions you might have. The important thing to remember is that with a little tune up work you can have a very reliable carbine that is tremendous fun to shoot.
   It is important to remember that Pablo's build and my two builds are a little different.  Pablo's build is based on a lower that uses GG magazines. My builds both use the QC10 lower and run Glock magazines.  Still, the work we did on our pieces was very similar with a few small variations.

  I wanted to clarify number 10 on my list. Pablo and I had been discussing the trimming we did on the two bottom feeding lugs of our AR's, even exchanging pictures. He pointed out to me that he had removed material from the rear of both lugs before polishing them, something I had not done.
  The idea here is that by removing the material you lower the height of the lugs and they taper up to full height at the front. This leaves plenty of material at the front to strip rounds from the magazine but allows the rear of the lugs to pass over the round in the magazine with minamal contact until the lug is beyond the crimp. Polishing means that as the two lugs scrape across the top of the magazine round they have very little friction or drag. Because of this, they also tend to move the magazine very little. All this contributes to a much smoother feed, ejection, ect.
  So, to trim your lugs you need to take material off the outside of both lugs, thinning them enough that they clear both sides of the magazine and lower the rear of the lugs so that they taper up to the front, which is left full height. Polishing all contacting surfaces insures minamal drag.
  I left a little height on the rear of my lugs so that they will somewhat lock into the barrel extension lugs, but I don't believe this is a huge consideration because the lock, designed for a .556 round, is more than strong enough to handle the 10mm.

I keep thinking I'll have time to add detail and I just can't catch a break.

Quote from: Pablo on February 17 2016 06:49:53 PM MST
I keep thinking I'll have time to add detail and I just can't catch a break.

Wow Pablo, you seem to be a busy guy! That's why I updated the list. But, the board will be here next time you have some time.

Quote from: Pablo on February 17 2016 06:49:53 PM MST
I keep thinking I'll have time to add detail and I just can't catch a break.

Pablo,
  Now that you have your 10mm running so well are you still looking at doing the 9x25?.
  I've got to say that the 9x25 is a great intermediate carbine round.  More versatile than the 10mm with almost as much close range stopping power and better gas pressure to run the AR. They are both a hoot to shoot!

Quote from: mrpipesmkr on February 27 2016 10:46:21 AM MST

Quote from: Pablo on February 17 2016 06:49:53 PM MST
I keep thinking I'll have time to add detail and I just can't catch a break.

Pablo,
  Now that you have your 10mm running so well are you still looking at doing the 9x25?.
  I've got to say that the 9x25 is a great intermediate carbine round.  More versatile than the 10mm with almost as much close range stopping power and better gas pressure to run the AR. They are both a hoot to shoot!

I've been meaning to do exactly that now that I FINALLY have the 10mm running. I need to see what kind of package deal he can do. Must send email soon. See if I can have him adapt my AIM ultralight bolt and throw a GG mag in the deal. I'm going 16" barrel on this one. Underwood has 9x25 FMJ back in stock. I'm saving all that brass and will make brass do. Oh this is gonna be good.

  I wanted to mention another problem I had when using the Korean, KCI .45 auto magazines in my 9x25 build.
  As most 10mm and 9x25 shooters know, these magazines can be converted from .45 auto to 10mm/9x25 by simply adjusting the feed lips down to the 10mm diameter. Usually this is enough to convert them although sometimes the spring has to be adjusted also.
  There is another problem that comes up when using these magazines to feed 9x25. Occasionally a mag That feeds 10mm perfectly will jam when feeding 9x25, with the rounds becoming stuck at the top of the mag. In some cases you can have as few as 3-5 rounds in the mag When this happens.
  The problem is with the shoulder of the 9x25 round. If you take apart the KCI mag You will see that there is a slight ridge stamped into both sides of the sheet metal of the mag Located at the top of the mag. These two ridges contact the front portion of the 10mm brass and guide the round into the feeding lips. However, the 9x25 brass is not straight like the 10mm is since it has a shoulder where the case drops down to 9mm. This 9mm part of the case happens to contact the ridges in the magazine rather than the 10mm section allowing  the rounds to angle off 1mm to each side causing a jam.
  The easiest solution is to take the magazine apart and extend the ridges on each side of the mag back toward the rear of the mag by using J.B. Weld.  It doesn't take much to extend the ridges back far enough that the 10mm portion of the case is contacting them. This forces the rounds in the upper portion of the magazine to set straight in the mag and move properly into the feed lips eliminating this kind of jam.
  Hopefully my discription here of the problem and the solution is clear but if you take your KCI mag apart and put a 9x25 round int the upper section you will see where the case is contacting the ridge. Compare that to where a 10mm case contacts the ridges and the situation becomes evident.

 

Pablo,
  Had a chance to go to the range Sunday afternoon. Had a little wind and a few sprinkles but a nice cool day for the range.
  My son in law and grandson came along and we took several pistols and rifles. Don't want to even think about how many rounds of various caliber see went through but I do know we put 150 rounds each through the 10mm AR and the 9x25 AR.  We had one hang up on the carbines when the 9x25 failed to feed one round by hand cycling. Dropping the bolt release and during firing it fed perfectly.
  My main reason for going to the range was I wanted to zero both builds at measured distances. We used 100 yards as a zero for both the 10mm and the 9x25 and adjusted for drop further out, as far as 200 yards. As I've said before, I am impressed with the accuracy of both builds. We found it fairly easy, even with a little wind, to shoot 2-2 1/2 inch groups at 100 yards with the 9x25 doing a little better than the 10 in the wind. The two stage triggers I'm using on my builds really helps and having a good table to rest on makes quite a difference. At three hundred yards my groups did grow quite a bit, out to 3 1/2 - 4 inches with several fliers I prefer not to talk about!  I have to attribute this to a shaky old man with old eyeballs. My grandson did better but I haven't admitted it to him yet!
  It seems both of our builds are pretty well dialed in now. I'm starting to have confidence that when I pull the trigger on mine they are going to go bang every time!  Now I just need to find a couple of hogs to volunteer for a little ballistics test I have in mind!

Wow awesome. I try to hit steel at 200 yds with my 10.5" 10mm. THAT is not a given!!

  Well, my 16 inch barrels probably help accuracy a little, but your shorter barrel should turn in comparable groups.  We took the red dot off my 10mm and put a decent variable on it. I had the advantage of having some young eyes along with me to do the dialing in. My old eyes require some concentration that my grandson doesn't have to bother with.
  One thing I have noticed is that when shooting a large, general target like a steel your groups will fall off. It's psychological I think.  Because you are shooting for a hit anywhere on the steel you tend to not focus down like you will with a decent Bulls-eye target.  Just natural l think, but if you try shooting at a bulls-eye target at the same range you'll be surprised at how things tighten up for you.
 

Quote from: mrpipesmkr on March 09 2016 05:32:10 AM MST

  One thing I have noticed is that when shooting a large, general target like a steel your groups will fall off. It's psychological I think.  Because you are shooting for a hit anywhere on the steel you tend to not focus down like you will with a decent Bulls-eye target.  Just natural l think, but if you try shooting at a bulls-eye target at the same range you'll be surprised at how things tighten up for you.

This SO true. I'm just thinking I can hit, don't bare down and remember all the fundamentals!

Giving this a bump for the recent interest (inside and new folks) for 10mm AR feeding issues.

Can someone help me understand what is done to a BCG to allow for a 40/10mm case to be used.  Specifically the bolt face on a DI bolt.

Quote from: 10fanatic on January 27 2017 01:21:36 PM MST
Can someone help me understand what is done to a BCG to allow for a 40/10mm case to be used.  Specifically the bolt face on a DI bolt.

Almost the same dimensions as a 6.8SPC bolt face. The ejector has a slight angle and is polished. The extractor has some material removed and is polished. The trailing edge of the lowest lug is slightly rounded and all lugs polished - the lugs do very lightly contact the next round in the mag, but you don't want the bolt to hang on the case mouth lip. (Never a worry with shouldered rifle rounds like .223 or 6.8) You can do a manual fit up with an empty case.....a lot of this is trial and error.

Thanks Pablo... Couple more questions...  Where in the heck do you find 10mm barrels with gas holes for DI?  All i can find are back preasure barrels. 

Also, for any reason would a 6.8spc side charging handle upper and bcg NOT work?  Just thinking about ideas and generating knowledge. 

Thanks!

Quote from: 10fanatic on January 27 2017 08:58:07 PM MST
Thanks Pablo... Couple more questions...  Where in the heck do you find 10mm barrels with gas holes for DI?  All i can find are back preasure barrels. 

Also, for any reason would a 6.8spc side charging handle upper and bcg NOT work?  Just thinking about ideas and generating knowledge. 

Thanks!

Only RMW. No one else makes a 10mm DI AR - as you can tell by this thread, it's no cake walk.

The bolt carrier will need to be adapted to the magazine feed lip width.

 ;D Forgot to post this:

(http://pws.cablespeed.com/~pablomail//engrave2.JPG)

Awesome Pablo


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Quote from: sstewart on May 23 2017 08:57:32 PM MDT
Awesome Pablo


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Thanks - I now have a decent stockpile of full power 10mm ammo!

So this pup was sitting in the safe for awhile.......took in out for the waguns.org New Years day shoot and it ran like crap. Not sure what I forgot, or what I was doing wrong - misfeeds all over the place. Seemed like magazine problems. Ugg.

One thing I forgot was I had a super light recoil spring. So I changed out to an HD one (both flat wire). Thought here is the rounds need to be driven fully home.