Optimum OAL for a G20 gen 4

[Kenk]

When using new starline brass and 180gr XTP's, what would be the optimum OAL for overall reliability 1.255?

[The_Shadow]

1.2500" for almost every thing...  here is why.

The usual round nose FMJ (as in 45ACP 1.2750"Standard) because the full nose is there.  The 10mm when it came about used truncated cone designed projectiles, which had the nose already shorter due to the flat point or hollow point designs, this already made the COL shorter at 1.2500" to maintain the tipping angle equal to the longer round nose FMJ's and they still fit the standard interior of the magazine tubes.

Yes people have loaded longer COL to 1.2550" - 1.2600" allowing for slightly more power room or lower pressures.  What can happen in the magazine is the bullet nose can drag on the interior of the magazine tube, causing less spring tension to the upper most cartridge as it is being fed and longer loaded can strike the barrel chamber such that the tipping angle starts to add friction hampering feeding as the cartridge head tries to slide up the breech face and chamber fully.

These slight increases in friction here or there, can be the difference in proper feeding or stoppages or failures to go fully into battery.

Also the Wide Flat Nose bullets 0.3000" Sharp MEPLAT and wider may require even shorter COL to maintain space inside the magazine tube and proper clearances for tipping angles unimpeded due to their wider MEPLAT with respect to the angle measurements.

[Kenk]

So, if I find that I have feeding issues with some of my earlier loads with a COL of 1.2600, shorting them to 1.2500 shouldn't be an issue. The question is this (possibly a dumb one : ), Is there any need to re-crimp them with my standalone Lee crimp die after bringing them down to 1.2500?
Thanks for your help on this   


Ken

[Spudmeister]

1.2500" for almost every thing...  here is why.

The usual round nose FMJ (as in 45ACP 1.2750"Standard) because the full nose is there.  The 10mm when it came about used truncated cone designed projectiles, which had the nose already shorter due to the flat point or hollow point designs, this already made the COL shorter at 1.2500" to maintain the tipping angle equal to the longer round nose FMJ's and they still fit the standard interior of the magazine tubes.

Yes people have loaded longer COL to 1.2550" - 1.2600" allowing for slightly more power room or lower pressures.  What can happen in the magazine is the bullet nose can drag on the interior of the magazine tube, causing less spring tension to the upper most cartridge as it is being fed and longer loaded can strike the barrel chamber such that the tipping angle starts to add friction hampering feeding as the cartridge head tries to slide up the breech face and chamber fully.

These slight increases in friction here or there, can be the difference in proper feeding or stoppages or failures to go fully into battery.

Also the Wide Flat Nose bullets 0.3000" Sharp MEPLAT and wider may require even shorter COL to maintain space inside the magazine tube and proper clearances for tipping angles unimpeded due to their wider MEPLAT with respect to the angle measurements.

Thanks Shadow,  I have had some totally unexplained failures to feed with the 180gr XTP bullet and your explanation makes more sense than anything else I can come up with.  Plus, I run my 200gr WFN bullets quite short and they feed 100%.  TY