Carbon or a shot out barrel?

Smokerroller

Si vic pacem, Para bellum
Full Member
Minuteman
Jan 23, 2013
394
66
Sheridan, WY
These photos are from my 6.5SAUM with about 350 rounds on it. The bad pictures are from an inch or two after the throat. The good picture is middle of the barrel. Is that just carbon or is that fire cracking of the steel? Should I keep trying to scrub it out or is it part of the barrel steel? Accuracy has been satisfactory, ES and SD have never been good so can’t speak to that.
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Lands are starting to show some firecracking. Probably only have a good 500 - 750 rounds left on her :D . When velocity drops considerably or accuracy goes away, that is a better time to determine when she's shot out.

As far as the carbon buildup; it is certainly there. Nothing that some careful cleaning won't alleviate though.