Jason:
Todays SAAMI standards ( 1992) are essentially the same , except for some statistical methodology, as the 1925 SAAMI standards.
A post 1924 - designed American double gun, by a major manufacturer ( Ithaca , LC Smith/Hunter Arms, Parker, Winchester) will stand the pressures of modern shells just fine.
What may cause you grief will be the recoil shock - the impact from heavy loads at high velocities on a stock head that may be oil soaked, punky, or cracked from years of abuse. Make sure the stock is sound. Or you can shoot loads that are a little less zippy - Ill bet dollars to doughnuts, and have the ballistic data to back it up, that the 35 yard duck you are shooting at cannot tell whether the muzzle velocity of the 1-1/4 ounces of Bi/Sn you have launched at him has a muzzle velocity of 1150 or 1350, but your shoulder and the stock head can tell.
Reloading is a great way to tailor the load to the game.
Regards
GKT
