What happened, after the advent of "modern" smokeless loads in the 20's, was that ammo makers started putting two warnings on their shotshell boxes: Don't shoot in guns with Damascus/twist barrels, and don't shoot in guns with chambers shorter than 2 3/4" (assuming that was the length of the shell in question). Those warnings made sense, not because Damascus was unsafe with smokeless nor because the extra 1/4" hull length was a problem in and of itself, but because those modern shells could develop higher pressures than those which Damascus/short chambered guns had been built to withstand.
Eventually, those warnings were (incorrectly) translated to mean that no smokeless loads are safe in Damascus guns, nor are any 2 3/4" loads safe in guns with 2 1/2" chambers.
