Careful with what ammo you land on,if said shotgun is damascus twist "not suitable" for modern shot shells shotgun makes a good coversation piece,even bismuth would'nt be a good choice because of "fps" loads,however as stated above flycarpin is spot on with hevi shot classic doubles made excluvely for older shotguns/side x side double barrels back in the day when shotgun manufacture'ers used a softer gauge steel to weld barrels together,hevi shot classic doubles is your "huckle berry" low fps also low recoil,if your old thunder stick barrel is damastic twist most often its stamped as such near the breach plus barrel fixed choke constriction as well,if worn off see a good old timer gunsmith.