Forgot to add....I shoot an ancient W.H. Hamilton double barreled hammer gun, with, no doubt, short chambers. Says:
>Twist Belgium< on the top rib. The old gent I bought it from, gave me several part boxes of the shells he used in it.
Yep! 2 3/4 High Brass Federals....... Remarked; "she kills ducks good, but she's a little too tight for pheasants; tears 'um up too much." I shoot suitable low pressure loads for hand-thrown clays........... Grant.