Joe's got the right idea with the steel wool bbl "lapping". I do that to all new bbls, too, no matter whether muzzy or breech guns. I unravel a bit of 0000 steel wool and cut it into about a 2" square. That goes on top of an oiled patch, and both go over a brass jag. The rod used MUST be stiff 'n' strong metal, brass or steel. It might take some fiddling, but the idea is to get the combination of wool and oiled cloth to have a *tight* fit into the tube, where getting it in might take a mallet whack or two, and after that it'll constrict to the lands 'n' grooves and allow pushing and pulling by hand.