Outside or inside of the barrel? For the outside I've had good luck with 0000 steel wool with lots of WD40. Start in a spot that's not noticeable first to try it. Work softly at first with light pressure. There are no pictures but one of the mistakes IMHO is if the gun is kind of beat up they over clean the barrels . Then the overall finish doesn't match up. If that's the case don't over do it. Try to get an overall finish so the gun looks symmetrical .