For those with American vintage guns, it's probably good to remember that in the early days of SAAMI, which came into existence in the mid-1920's, there were different proof pressures for guns with short chambers vs those with 2 3/4" chambers. Hunter Arms proofed their 2 3/4" 12's at 15,900 psi and the 2 5/8" guns at 14,300. (Also worth noting here that what was recorded as psi back then--and this information is from the mid-30's--was actually LUP. Pressure testing back then was still done with lead crushers vs the current transducers.)
Re CIP proof testing, anyone interested in doing that needs to be aware that the British proofhouses may still be reporting the pressures at which they proof their guns in LUP rather than psi. They were still doing that back in 2001, when I communicated with the Birmingham proofhouse. Fortunately, when it was clear that there was a misunderstanding, they converted the proof pressure in question (and the appropriate service pressure, which is even more important) to the American transducer equivalents. Their proof laws have changed since then, and we may now be speaking a common language. But anyone having a gun proofed in the UK would want to make sure of that. They may give the pressures in (metric) bars rather than psi, but if you're going to convert from bars to psi as measured by transducers, you need to make sure that they're talking transducer bars and not lead crusher bars--which they were still doing back in 2001.
Last edited by L. Brown; 01/29/20 08:12 AM.
