rifle barrels for new Englanders can be found for 100 bucks or less so ya could buy a spare barrel & for about another 100 have it bored to smoothbore. due to the depth of the sight holes 12ga would probably be out but 62cal should be do-able. a couple fellers that do this for a livin' are Ed Rayl in West Virginia & Robert Hoyt in Pennsylvania. neither has a website but ya can go over to the muzzleloading forum & look around a bit to find their contact info if nobody here chimes in with it. luck to ya & have a good'en, bubba.