Thanks for all the info. I got the bore cleaned out, the bucket trick helped a lot! After removing half a sabot, a ton of old powder, rust, and gunk, and just working with it for a couple hours, I got the barrel looking great! The land and grooves are very well defined, and it shined up real nice. Then the jag broke off, with a chunk of old t-shirt wrapped around it, and is stuck in the back end of the bore. I still can't get it out, it's jammed good. But all the rust is basically surface rust. I'll have some pitting, but nothing too bad. I'm going to strip the barrel and re-blue it as practice for the kit I want to build. I think it'll make a fine rifle. Oh, and no worries, I'm taking it to a gunsmith that specializes in black powder. It just so happens I'm heading back to Oregon, and there's a muzzleloading specialty shop in my hometown that'll look at it.