Hey guys,

I'm currently experimenting with my 12 bore "slug" gun, and am looking at making some black powder loads for it. The projectile I will be firing weights 580 grains.

I've already used 102 grains (3 3/4 drams) Pyrodex RS powder with this slug, and would like to load something a little hotter. That being said, I don't know what my limit is regarding volume-pressure ratings, so figured somebody here might have some info on this. Basically this is a fancy way of saying what is my max load of black powder for a 580 grain projectile?

My slug gun is a 12 gauge Lanber Supreme SxS shotgun with 3" magnum chambers, meant to handle modern smokeless loads. It will manage 11500psi, in accordance with typical SAAMI specs. (I don't know how much of this is relevent, but figured I'd better leave more info than less.)

Thanks very much guys.