Here in the U.S., we have private pressure testing by some of the gun companies, and largely it is our lawyer population that assures we have very good barrels made in the U.S., rather than a Proof House as in Europe or the British Isles. The Proof Houses have had some very important criticisms over the past few centuries, and yet our own "Proof House", lawyers, have negated the need for an actual Proof House in the U.S.
I'm hoping you or others on this Forum can elaborate on European pressure testing, since so many MLs were and are made there. I'm very familiar with CUP and psi pressure testing and pressures as for modern firearms and also black powder cartridge guns, but have always wondered how the MLs are pressure tested under European proof laws where they measure in kilograms or BAR rating; namely, what are the European proof parameters for, say, a .45 and .50 ML barrel, and how can we Yanks extrapolate that to pressure measured by CUP or psi?
Then we can much better talk about smokeless powder and ML barrels.
Thanks and aloha, Ka'imiloa