Everybody seems to have a favorite "snake oil" to clean copper fowling and most cost $2-$4 an oz. It is my understanding it is the ammonia in the "snake oil" that dissolves the copper. It is also my understanding that the ammonia will not hurt the barrel, some let it soak overnight. So, why not use straight household cleaning ammonia at $2 a quart? just asking Bill "Hey, I'm in FL with nothing to do"