I have a Ruger SS single six convertible revolver that has had a blackened face on the .22 LR cylinder since I received it years ago. Decided I wanted to try to clean it over the weekend. I tried my CLP cleaner, Never Dull, Dremel buffer, nothing hardly touched it. Then I decided to try a small piece of scotch bright and some CLR. Since it was a milled surface, I figured it couldn't do much harm. It cleaned up with very little effort, and now looks nearly new. I'm certainly not suggesting CLR for cleaning your firearms, but for this purpose on an unpolished surface, it worked great!