--- snip --- and stamped guns didn't actually have pressure read for proof, but survived firing proof cartridges.
Largely correct. Both transducer and crusher methodologies require the test barrel have a hole drilled into the chamber to grant access to obtain the pressure measurement. It's hard to sell a gun with a hole in the chamber :-)
Preliminary or first proof (testing of barrels alone) and final or second proof (testing of the assembled barrels and receiver) is done by firing one or more proof cartridges and examining the barrel/assembled action for unacceptable changes. If no unacceptable changes are found proof has been passed; if unacceptable changes are forum proof has been failed.
The pressure number we find on the barrel flats of a gun identify the pressure standard applied to that barrel/assembled action and do not indicate the pressure actually attained in that gun during proof.
