RE: JB's Bore Cleaner
Mark - I use it with some degree of regularity. I also use a product called USP Bore Paste, which appears to be just a little bit finer than the JB. I mainly use it for deep cleaning rifle barrels when they get significantly fouled with copper or hard powder residue. Sometimes for barrels that start out a little on the rough side. As mentioned, you only use this stuff after getting the barrel as clean as possible with conventional solvents/brushes/patches. Moderation is the key.
I normally wrap a patch around a brass brush one size smaller than the bore. Work the area just ahead of the chamber quite a bit more than the middle - and don't do much lapping in the last two inches. I really recommend a Hawkeye Bore Scope when using these kind of products - it will tell you when to quit and what areas of the barrel need additional attention. Clean it out with Gun Scrubber - followed by brushing with Shooter's Choice and then wet patches.