black powder chamber pressures.

[mooncoon]

One thing that properly compressed black powder loads do well is obturate the bullet, due to their high pressure spike

. That being said, I am extremely doubtful that anything under 15,000 psi peak pressure will be sufficient to obturate the bullet.

In looking through Lyman's black powder manual at pressures for muzzle loaders, the highest pressures in 45 cal they seemed to be getting were around 15000 CUP. I suspect that pressures in small caliber cartridges such as the 32-40, the pressures might go a little higher say 20,000 but not much higher. I have a rifle now with the bore .007" oversize, and slugs cast with 5% tin/antimony are definitely obturating in that gun. Tempered .321 bullets keyhole, bullets from roughly 50% wheelweights keyhole about 1 in 5 plus lousy accuracy, bullets from 5% group reasonably well and non keyhole. I am guessing that the pressure is in the 15-20,000 CUP range

cheers mooncoon