I use two things to remove copper depending upon how quickly I want to remove it. If I have all night I use wipe out foam and let it sit over night. If I need it done quickly the I use KG-12, it works better than any ammonia based cleaner I've seen.
Neither will really tell you if the bore is free of copper. I've found the best way to tell is a flashlight shined in the muzzle end.
