There is no material in a bore snake that is harder than the inside of a barrel to make a scratch. If you are seeing scratches on the inside of your barrel after using a bore snake, it might be trails of brass or copper from the bore brush’s bristles. It should come off with a bit of shooting and then cleaning it afterward. It might also be because there is sand or fouling that regular bore snake can’t clean. You will need a cleaning rod to deep clean it and remove the scratches.