First better look at the chamber, some were 2 inches or 2,5 maximum. Then have good gunsmith, who know really well it's job, look about the locking.
Then look at the muzzles. Generaly these old shotguns have very tight choke that were right with BP powder and fiber wad with relatively light weight loads. These muzzles don't stand very long the pressure of heavy loads with plastic wads.
Even if some of the damascus barrel can stand smokeless powder, better stay in the low pressure light loads and avoid definitively the 3 and 3,5 cartridges. And never shoot steel inside. If they stand it they will not last long.
In Europe we have expensive british ammo from Eley or under Purdey name or french one specialy made for 65mm hull at very low pressure that can go in these barrels. May be Gamebore makes some too. In USA i don't know. But as the saying goes: better safe than sorry!
Dom
