Use Montana Xtreme Copper Killer. Wrap a soaked patch around a nylon brush (can be undersized) and brush it through the bore let sit 1 hour. Again use the nylon brush/patch (dry) and push through the barrel. If you get blue there is still copper in there. What solvents have you been using? Some times if the bore is really fouled, the copper may be layered in there. I typically use Wipe Out or Patch Out and let it sit over night. For really bad copper fouling use Copper Killer and let sit over night (it is oil based and will not pit the barrel). Good luck.
