If all else fails, and I do mean all else, I used this to clean an abused cannon barrel. Janitorial supply can get I believe 10% ammonia. Combine 3 parts of this with 1 part ivory brand dish soap. Do this outside. Scrub bore with this solution on a nylon brush, allow it to set 5 minutes, and rinse with water. Inspect bore, and repeat as necessary. When everything comes out to your satisfaction, rinse well with water, rinse with white vinegar, and then rinse with more water. Oil the bore VERY well after this point, as it is extremely suseptable to rusting. The ammonia solution will destroy a brass brush. Don't ask me how I know. This is nasty stuff, and should be done with outdoor ventilation, and protective clothing. It is my strongest recommentation to protect any finish on the exterior of the gun when performing this process. Good luck, and good shooting,
"It is not the critic who counts, not the man who points out how the strong man stumbled, or where the doer of deeds could have done better. The credit belongs to the man who is actually in the arena, who's face is marred by dust and sweat and blood, who, at the worst, if he fails, at least fails while daring greatly, so his place shall never be with those cold and timid souls who know neither victory nor defeat."