What you have is a Thomson Center muzzle loader. It sounds like you would like to have a Hawken rifle. Seeing what you have done, so far, I would say you are about ready to get a book or two about Hawken rifles, then buy a lock then a new barrel, stock butt etc. and build one. Keep the old one even if you never shoot it after your build. In ten or fifteen years, you will be glad to have both of them/
