I've only used it on two rifles, and both have SS barrels on them. I was REALLY careful to put a rag over my stock and a bore guide to keep things off any other surfaces.
We used it on the fuel gas rings of our gas turbine to remove the carbon in them after having some hydrocarbon issues arise giving us some premature ignition in the rings. It cleaned them up so well I figured I had to try it in my rifles as well. Right, wrong, or indifferent, it cleaned out the carbon in them like now, and that stuff is VERY difficult to get out even with some of the best carbon dissolving gun cleaners. It forms a ring inside the throats and eventually will build up to the point it makes chambering hard. The Carbon Off, knocked it out after little to no time. Then I followed up with regular cleaning and oiled everything up when done. I have noticed anything which shows it has hurt the inside of the chamber, throat, or barrel to this point. I do however admit I have only used it a couple of times so who knows what long term effect it may have. I will probably shoot out both barrels long before it shows me anything.