I had one of those barrels. My mom bought an 1879 Trapdoor rifle for me at Cash Box Pawn Shop, Tucson, Az back in 1971 for my 14th birthday. It was like new, and had Bayonet, scabbard, Steel pistol grip, and an a beautiful original black leather sling. There were 2 pawn shops side by side just outside of the main gate of Davis Monthan AFB on Wilmot Avenue. The other was the Gold Spot Pawn Shop. I was always in there looking at the guns the Airmen pawned off and never came back for. Anyway The muzzleloader conversion barrel was unmarked, and came with an original 1863 case hardened hammer. I shot it quite a bit after I bought a Lyman .45 cal Mini ball mould. In my Senior Year at Palo Verde High School The machine Shop Instructor Mr James Bishop let me convert that muzzleloader barrel into a Trapdoor for a super chance at an A+ for the year. He also wanted me to duplicate, all the other parts needed to build a complete gun. except the breech block, receiver and hammer, which I ordered from DGW. The Wood Shop Instructor let me make the full length stock in his class. I had to use maple lol. Anyway I got my A+'s The bore was better suited for .451 / .452 bullets and the twist was 1 in 66" Man could that thing make those light bullets fly like an express, and it was accurate. Different days back then. We even had a school gun club.