If you are concerned about those chatter marks get that kit of abrasive coated bullets (the name escapes me at the moment) and follow instruction. There have been many posts over time about them and I don't recall anyone saying they damaged a barrel. In fact if memory serves, the comment was that they did not have to use the whole kit of coated slugs to clean up the barrel. Most reported their barrels were easier to clean and accuracy improved.

El Lobo.