My Father, Grandfather and Uncles were all convinced that those Damascus and Twist barrel warnings were just an attempt by the manufacturers to scare consumers into buying a new gun. I know my Father's 1896-vintage AE-Grade Remington Hammerless Double and my Grandfather's 1890-vintage PH-Grade Parker Bros. double both digested many, many, cases of Super-X and Federal Hi-Power shells over their lifetimes. Dad's AE-Grade is still looking fine in my gunroom. He shot it up to when he quit hunting in 1988 after he turned 81.
For two or three decades now I've heard this moaning over modern "SAAMI" spec ammunition. But, I've never seen any definitive information on what the pressure specs were for earlier nitro powder loads like say 3 1/4 drams of DuPont (or Schultze, or E.C., or Hazard, etc.) bulk smokeless powder and 1 1/4 ounce of shot, or say 26 grains of Infallible (or Ballistite, etc.) dense smokeless powder and 1 1/4 ounces of shot??? I have an early Western Cartridge Co. brochure on their Super-X load, and it says with their new progressive burning powder they are achieving this level of performance at lower pressures. But, I think that means a 3 3/4 dram equiv. load and 1 1/4 ounce of shot, while with the older bulk smokeless powders the heaviest 12-gauge loads offered were 3 1/2 dram.