GREYBEARD - The cases were made by Rocky Mountain Cartridge from a chamber cast of the gun. The guy there says they are good for 20,000 psi. Per conversations with AA Powder Company it appears my 720-grain slug at 1,000 fps is no more than a 12,00 psi load. By the looks of the primers it is considerably less than factory 20-gauge shells. Anyway, I think the guns and brass will take a lot more than my mild loads. They are fun to shoot though. A 720-grain slug at any velocity has a lot of momentum and kicks up a lot of dirt. I will post another Big Bore topic on the .50-140. - DON