Mike, there were no agreed-upon service pressure and proof standards for ANY shells or guns in this country prior to the creation of SAAMI. So . . . none, period, prior to 1926. That's not saying that gun and ammo makers didn't proof test their products; just that there were no common standards (contrary to all the other countries in the world with proofhouses).
Proof standards appear to have remained somewhat in flux, at least for a few years even after the establishment of SAAMI. LTC Calvin Goddard, I believe recognized as a ballistics expert back then, writing in "Army Ordnance" in 1934, stated that Hunter Arms proof tested 12ga 2 3/4" at 14,300. He adds that Parker followed "SAAMI standards": Proof pressure of 13,700 psi for 2 5/8" 12ga, service pressure of 9500 psi. 2 3/4" 12ga: Proof pressure 15,900 psi, service pressure 10,500 psi.
Good question about LUP vs psi, and when you go back to that era, you might well assume they're talking LUP--since that was what they actually measured then (although they called it psi). That would put the proof pressure of the 2 5/8" 12ga, following SAAMI standards, at around 15,000 psi; of the 2 3/4", around 17,000. Service pressure 10,500 psi and 11,500 psi respectively--which puts us at the current standard, with 2 3/4" shells. Additionally, Arthur Curtis--who worked at one time or another for a number of American firearms makers from the late 19th century until at least the 1930's--gave service pressure for the 2 3/4" 12ga at 9,000-10,000 psi, quite close on the upper end to current standards, assuming he was dealing in LUP.
Hope that helps.
Miller, I didn't say that the Super-X was the first 2 3/4" shell. I'm quite well aware that there were guns chambered at 2 3/4", and shells for them, before the Super-X appeared. However, it is generally accepted as the first MODERN 2 3/4" shell, using progressive burning powder. It was also a shell which increased pressure (by at least 500 psi, per Curtis) increased standard field payload to 1 1/4 oz, and increased velocity. Curtis refers to "high speed shot shells" introduced years prior to his 1938 American Rifleman article, and I'm pretty sure those are the ones he means. They certainly received a lot of glowing press, from people like Buckingham, and accelerated the changeover to 2 3/4" as the American 12ga standard. And it seems odd to me--since we certainly agree that increased payload + increased velocity = increased recoil, and since we also agree that increased recoil is not a benign force (at least on the stock, if not on the metal)--that SAAMI would stick to an antiquated service pressure ceiling rather than establishing a payload/velocity standard to protect our guns. Perhaps pressure still remains key, however much recoil has increased--and it certainly has, since WWII.
Rabbit, you're constructing a nice straw man there. I certainly never stated--and I don't believe ANYONE has stated--that increased pressure = increased recoil. In fact, if you go back the line a ways, I believe you'll find an example I gave of two loads that are identical in payload and velocity, one significantly higher pressure than the other--even though the higher pressure load uses a lighter powder charge. Powder burn rate has a whole lot to do with pressure . . . which is why, unless you reload, you can't be sure at all about pressure other than that it's within the maximum established either by SAAMI (US ammo) or CIP (European ammo).
