I have never seen any indication that any of the US makers changed their guns when the new higher pressure shells were introduced in the 1920's, with the exception of Ithaca. The Drawings and Specifications book for LC Smith shows only one barrel change, and that was for the featherweight 12 in 1912. SAAMI was established in the mid 1920's as I recall, and about the same time Hunter Arms started putting their proof mark on the LC Smith guns. I don't know what the earliest SAAMI specs were for shotguns, but today. the pressure specs are the same for a given gauge regardless of the payload in both 2 3/4 and 3 inch shells. The 3.5 inch 12 ga calls for higher pressures however.
