i called and got replies from Noveske, Arrow Precision, and others and some said Brake Clean can be used, hopps 9 can be used, others said no you should never use brake clean and only CLP. MY guess is, I know alot of people use brake clean and if it was so harmful, you would have barrels coming back wrecked. I usually use brake clean followed up with hopps 9 even before it dries, my barrels look fine and shoot very tight groups. I will probably buy spare barrels one for each in case and to be on the safe side.