I took my S&W Governor out for its first firing last Friday. I shot .45 ACP's. When I went to clean the cylinder I discovered some rings of crud inside of each chamber just in front of where the mouth of the brass would be. I've tried everything that I can think of to get those rings off but nothing seems to be working. I've tried foam, a brass brush with bore scrubber, Remington bore cleaner, and finally lead removing cloth wrapped around a brass brush. The lead removing cloth seems to work to a fashion but it is taking a lot of working at it and I am hesitant to do too much with that method. I am afraid that I am damaging the cylinder. Any ideas would be appreciated.