You are getting a lot of advice as to different chemicals to put in that barrel, and this could be disastrous. Unless you're a chemist I wouldn't put anything in that barrel that wasn't made for it. Furthermore, I strongly suggest you speak with one of the barrel manufacturers about how to handle this. I spoke with Frank Green at Bartlein, and I promise you he did not suggest I use any of the things I've seen suggested. His suggestion is soak the throat with Hoppes #9, overnight and then use a patch wrapped brush to short stroke the throat. He also said JB Bore Compound, not Bore Brite, to help remove the stubborn carbon, followed by Hoppes. He said there are a lot of chemicals that can etch or pit the barrel.