Is the gun shooting badly? I know that in the magazines that I have read in years past this is one area that some swear by having thier barrel a bit fouled to maintain accuracy, and some swear by an ultra clean barrel to maintain peak accuracy. I am not sure which to believe since I just clean my guns after a couple of boxes of shells. More to keep them from rusting during storage than for accuracy. I dont know which solvent is best to get the copper out but I will wish you good luck on being able to get the rifle back to good condition.