Like most things in this country--since, for better or worse, we don't have a govt proofhouse--the conversion from crusher to transducer measurements didn't happen all at once. (Didn't really happen all at once in CIP countries as either. And to further complicate things, at least some of those countries--including England--continued to mark their guns with crusher values, like 850 bar, long after they'd converted to using transducers. In fact they never used transducer-derived proofmarks. When they dropped the "bar" proofmarks in 2006, they replaced them with STD for standard proof and SUP for superior proof.)
Meanwhile, in this country, I have a copy of the Lyman Shotshell Handbook (Third Edition) from 1984. When I go to the reference section, I find a long discussion on pressure--and on the crusher method of measuring pressure. But at least all the pressure readings were listed as LUP and not psi.
Last edited by L. Brown; 10/28/14 08:08 AM.
