I use
Montana X-Treme Copper Killer. Just follow the directions and it works like a champ.
From their FAQ:
Q. I have always heard that ammonia is hard on barrels and will etch them. Your products have a strong ammonia smell – will it hurt my barrel?
A. Montana X-Treme solvents contain ammonia in an oil base and will not hurt or etch the barrel. It is safe to wet patch and “soak” the bore for problem barrels or stubborn copper deposits. Soaking the barrel with Bore Solvent or Copper Killer for an extended period will not harm your barrel.
The front of your cylinder can easily be cleand up with any "Lead Away" cloth.