Through the years, proof loads have been determined by various means, but usually are designed to be 25-30% over the standard operating pressure. That should be good enough; the goal is not to blow up brand new rifles, it is to ensure that they won't blow up with the standard load.
Springfield Armory not only proved the finished rifle, but also proved the barrels before assembly and even proved the barrel billet before it was machined. The purpose was to detect and weed out flaws at the earliest point, before time and money had been wasted completing a barrel and assembling a rifle only to have the barrel fail and destroy the receiver, stock and other expensive parts.
I had read that the same practice was followed by Mauser, but when I said that on a site devoted to Mausers, I was told that Mauser never proved any barrel until the barreled action had been fully finished and assembled. Maybe they proved at a lower pressure than Springfield did, or maybe they made better barrels or maybe they lost receivers, I don't know, but the Mauser experts assure me that no proving was ever done on barrels before assembly.
Jim
Springfield Armory not only proved the finished rifle, but also proved the barrels before assembly and even proved the barrel billet before it was machined. The purpose was to detect and weed out flaws at the earliest point, before time and money had been wasted completing a barrel and assembling a rifle only to have the barrel fail and destroy the receiver, stock and other expensive parts.
I had read that the same practice was followed by Mauser, but when I said that on a site devoted to Mausers, I was told that Mauser never proved any barrel until the barreled action had been fully finished and assembled. Maybe they proved at a lower pressure than Springfield did, or maybe they made better barrels or maybe they lost receivers, I don't know, but the Mauser experts assure me that no proving was ever done on barrels before assembly.
Jim