Never thought of CLR in a barrel before. I guess if it works in pipes, it'll probably work in the barrel. I have no doubt it is rust causing the residue on my dry patches. I can look down the barrel and see it between the lands as well as some minor pits near the bore. No matter how much I scrub with a brush, it's still there. I've never had it inspected by a gunsmith, so I don't know the extent of the rust or pitting down in the barrel. I figure worse case scenario I'll have to start shooting patched round balls. It hasn't come to that yet, and I keep it well lubed in storage now. My season is over next weekend, so I'll try it after that. Thanks.