Originally Posted by cowboy4evr
an old gunsmith told me if that happens , to use a piece of " chore boy " (copper scouring pad ) wrapped around an old bore brush dipped in some solvent will definitely clean it w/o harming the chambers themselves as Chore Boy is pure copper . For the solvent -- kerosene , Kroil , marvel mystery oil etc . Most Ace Hdwe Stores carry Chore Boy . Good luck
Improving on that idea: take a NYLON .38 bore brush on a 4" rod and chuck it in your hand drill. Take some scotchbrite pads and cut strips about 1.5" long. Wrap them TIGHTLY into the bore brush and force it into the cylinder tube. Use drill to spin and it will break down the hard carbon rings. For very heavy buildup, take some chrome polish and a Q tip and coat the burn rings and let that soak a few hours then scrub.