I own an old Colt 1878 hammer-double 12ga. in servicable shape.
Does have the Damascus barrels...does have a bit of pitting in the bores..and the tubes are amazingly thin at the muzzle.....
I looked at the chamber...and the old gun has a really deep/long set of chambers! A bit of casual measuring and comparing to modern shotguns..and I would say these chambers are at least as long as a modern shotgun 3" chamber..So I look at a old Crescent hammer double I own...It's got similiar long/deep chambers too
I had thought the golden oldies used 2 1/2" or 2 5/8" shotshells.
What lengths did the old late 1800's shotshells come in??