I do not know if this will help, but I had discoloration on my breech in my Staghorn. A person on this forum suggested a product called Nevr-Dull which I purchased at Wal Mart. My Staghorn has a nickel finish, and there was a stain which I believe was caused by the primer ignition. The Nevr-Dull did not remove all of it, but it did take a lot of the stain off the metal. I also use the stiff to clean the barrel, by wrapping a wad of it around a cleaning jag and scrubbing the bore if I feel it needs it. I also use it to clean brass on my traditional rifles..