I am shooting a shotgun that was made about 100 years ago. Its was made with cold roll steel, and has an imitation " Twist Finish"< but not a Damascus Barrel. Its was made in Europe, for sale through hardware stores here. Its chambers are for the European 2 9/16" cartridges, rather than our standard 2 3/4" cartridges. I have relieved the throats to allow a 2 3/4" shell to function properly.
However, I have never put anything stronger than a light 2 3/4 Dram equivalent shell through the barrels. Pressure on these 12 gauge shells is very low- in the 4,000 ft lbs range. The gun handles they quite well, and I am able to shoot my grandfather's shotgun instead of it gathering dust in some closet, or parking on a wall.
PLEASE, DO NOT "PROOF " THESE BARRELS ON YOUR GUN WITH ANY KIND OF STRONG LOAD! Remember, the length of the chamber has to accomodate both the length of the shell when it is loaded and roll crimped, as well as fit the shell when the cartridge is fired, and opened to its full length. The front of the shell that is crimped has to open up AND get out of the way of the shot charge in order to move out of the chamber and into the barrel, without causing excessive chamber pressure.
As with any person who is old, your gun deserves respect just for surviving so long, and kindness in how it is used. Perhaps the biggest work- out I have given my old shotgun is shooting a round of sporting clays with it. I don't do that often. It is a joy to bust clays, however, with such an old gun. :grin: :thumbsup: