Step #2 of the Black line.
Use Hoppe's Black High-Performance Copper Cleaner to remove copper residue from any firearm bore, especially high round count firearms bores. Available in a 4 oz bottle.
Hoppe's Black High-Performance Copper Cleaner is formulated with high round count firearms in mind but is suitable to use on any firearm bore. This copper cleaner is a superior formula engineered to remove high amounts of stubborn copper fouling from any firearm bore after a long day out at the range.