c. 1900 standard loads were actually heavier than today's, with very similar pressures. The “standard” U.S. 12 gauge Field and Inanimate Target load was 1 1/4 oz. shot with 3 1/4 Dram (1220 fps) of Bulk (DuPont, “E.C.”, “Schultze”) Smokeless in a 2 5/8” or 2 3/4” case, with a modern transducer pressure of 8000 - 9500 psi.
Live Bird loads were usually 1 1/4 oz. 3 1/2 Dram Bulk Smokeless Powder in a 2 3/4” or 3” (for additional padding) case, with a pressure of 11,500 psi
Just before WWI: The “standard” U.S. 12g Field and Target load was 1 1/8 oz. shot with 3 Dr. Eq. (1200 fps) Dense (“Ballistite” or “Infallible”) Smokeless in a 2 3/4” case with a transducer pressure of 8,500 - 10,000 psi.
20g period reported pressures vary significantly but 7/8 oz. 2 1/2 Dram BULK Smokeless was 8000-10,000 psi.
7/8 oz. 2 1/2 Dr. Eq. DENSE Smokeless was 11,000 - 12,500 psi.
ed's suggestion fails to accommodate for the weight of the gun.
Lower recoil in a vintage double is wise, and it's not hard to pick a foot/pound target based on the recoil calculation
1 oz. at 1180 fps (2 3/4 Dram) in a 7.5 pound shotgun = 17.3 ft/lbs of free recoil.
17 ft/lbs seems like a good target no matter if a 20g, 16g or 12g. Or maybe 17 ft/lbs for a 12, 16 for a 16 and 15 for a 20?
