Montana X-Treme Copper Killer is probably the strongest
ammonia based copper remover solvent on the market
today. The folks at Montana X-Treme report Copper
Killer to be completely barrel safe, and it contains no
amines, acids or chlorides. This solvent removes copper
fast, and is perfect for heavily copper fouled rifles. The
high ammonia content will react with bronze bristle
brushes, so they should be neutralized after brushing.
Nylon bore brushes could be a good alternative for this
solvent. Cleaning with Copper Killer should be done
outside or in a well ventilated location. This is a really
heavy duty copper solvent.
Sinclair, Issue:3B, Page:146