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.