No problem, Joe. As indicated above, Researcher is probably the guy most likely to know for sure. It's a mess to keep straight between all the American makers, because they didn't all switch to 2 3/4" as standard--and they didn't switch all their gauges (12-16-20) at the same time. The best I can do on Parker comes from a 1936 A&F catalog. They'd made the switch to 2 3/4" standard by that time on all 3 gauges.

As of 1934--according to an article in "Army Ordnance" that year--SAAMI had different service pressure standards for 2 5/8" 12's (9500 psi) and 2 3/4" 12's (10,500 psi). The current SAAMI 12ga standard is 11,500 psi--but I'm not sure when that was established.

Last edited by L. Brown; 02/15/20 07:55 PM.