Thread: Chamber pressure, expansion ratios and muzzle pressure

I would put the first step down at 8 inches and the second step at 12 inches from the breech, with both steps being radiused to remove stress points. You should bore the barrel to be only a 1mm wall at the muzzle. The major diameter should leave about a 2.5mm wall at the narrowest part of the barrel shank (ie: the bottom of the threads). Tricky work but quite do-able.