I am looking for information on the pressures generated by a 10 bore with a heavy African style charge (700 grain ball-1200 grain conical over 5-10 drams of black powder), but at this point I will take ANYTHING, and I mean ANYTHING that is remotely relevant to that. I have asked on the muzzle loading forum, shotgunworld, doublegunshop, and castboolits, without avail. Please somebody give me a hand. I am designing a 10 bore hammerless, under lever, and as I cannot afford commercially made barrels, or quality steels like 4140, and 4340, I have to improvise. Because of that I have to determine what pressure will be created by this thing, in order to determine if my barrel will survive. With what I have done so far I would consider 18000psi to be the maximum load pressure I will use in this thing. The math says I'm safe until 26000psi (and that's only the yield point of the steel), but I don't want to push it. Any and all help welcome, and appreciated!