Mike, I'm anxious to see Drew's response. However, I'm in possession of a magazine article on pressure testing (either "Army Ordnance" or "The American Rifleman, don't recall which--and I'm still unpacking stuff from a move) from the 1930's. All the pressure guns illustrated--and there are several, used by various companies--were of the crusher variety. Therefore, I've always interpreted anything from that era expressed as psi as being LUP--simply because everyone THOUGHT they were getting a reading in psi. I don't believe the term "LUP" even existed back then. (I'd be interested if someone could prove otherwise.) LUP is simply shorthand for a pressure measurement taken via the crusher measurement and originally expressed as psi.
Last edited by L. Brown; 11/19/14 05:42 PM.
