That 6mm with the tool marks shoots very well, it strips copper over those tool maks very well, too. That's about all tool marks are good for, collecting bullet jacket. Accuracy starts going down hill in 6-7 rounds. I don't have that problem with any Harts/Kriegers/Bartliens/Brux barrels that I've used. I don't find tool marks in any of them. After a short 'break-in', any of those settle in and a 60rd. LR Sporting Rifle Match can be fired without cleaning. That 6mm Shilen had 75rds. down it when I sold it (for a reduced price because of the tool marks). The new owner has another 350 rds. through it, and it still has the marks and fouls in the same place with the same result, degrading accuracy in less than 10rds.