I'm working on a 10mm shotshell. So far it works well in my 10mm revolver and loads and works well in my semi-auto. In the semi-auto it has to be single loaded as it is too long to fit in a magazine. I'll eventually cut the shot capsule down to try to get it to feed. I'm using 10mm magnum brass necked down in a .357 sig sizer die. A .38.357 Speer shot capsule loaded with no. 12 shot. The powder is W231 and I am using an over-powder wad made from a plastic water jug.
(http://i19.photobucket.com/albums/b188/Elmino1/IMG_3510_zpslg6xpgvt.jpg) (http://s19.photobucket.com/user/Elmino1/media/IMG_3510_zpslg6xpgvt.jpg.html)
(http://i19.photobucket.com/albums/b188/Elmino1/IMG_3511_zpsyfhsvfra.jpg) (http://s19.photobucket.com/user/Elmino1/media/IMG_3511_zpsyfhsvfra.jpg.html)
That's really cool. Thanks for sharing that with us.
Register it before CCI sees it
I made some for the 40S&W with the 9x25 Dillon sizer and 10mm case. I need some longer cases to do the 10mm shotshells. I used Red Dot powder and #6 (big and less pellets) but have #9 shot for the next run...there two paper wads over the powder, packed with the shot and capped with a gas check.
(https://s20.postimg.cc/mevushegd/IMG_0006_zpsxq49t5ib.jpg)
(https://s20.postimg.cc/3mjzowprx/IMG_0005_zpsyuyesg7w.jpg)
http://10mm-firearms.com/reloading/40sw-snake-shot-load/ (http://10mm-firearms.com/reloading/40sw-snake-shot-load/)