My own mini proof house
Just for comparative value, in the past I have obtained the actual measured tensile strength of a bunch of guns, then, with a few sectional measurements I did compute the supposed internal pressure at which the barrel explodes under hoop stress - from that value we then derate the numbers by whatever safety value we need.
So, here is what an old Mannesmann special steel double barrel assembled in Belgium gave me.
measured hardness of about 140 HB scale
steel tensile strength converted from measurement: 70000 PSI
unsafe blowup pressure at about one inch beyond the chamber: 21000 PSI
derated by a 50% safety factor (as an example): 10500 PSI
unsafe blowup pressure at the rim: 34000 PSI
unsafe blowup pressure halfway down the barrel: 12000 PSI
unsafe blowup pressure before choke area: 11000 PSI
The 70000 PSI tensile strength is very soft as we could imagine with something of a decarbonized steel. The evidence of the softness on this gun is also visible in the deep stamps of the proof marks and many nicks. It is not a heavy gun at all either.
I found this interesting.
Be safe.
