6.5x47L Bore ?

[daj]

When viewing my 6.5x47L bore through a borescope after 400 rounds, I noticed what looks like narrow glazed carbon strips in the grooves mid-way between the lands. The strips start at the throat and continue up the bore for quite a few inches before gradually disappearing. Either side of the discolored strips the grooves are spotless.

Over the same length, the lands also appear to be discolored from heat/pressure/carbon but otherwise are in good shape.

Is it possible that the grooves are not of uniform depth across their full width and the strips are the only part of the groove in contact with the bullet OR is this pattern normal?

Thanks.
daj

 

[SF340Driver]

This is actually not uncommon. It is harder to get the groove clean as the pressure from the patch is on the lands. You will usually see carbon left in the land/groove corners, but with some barrels it shows up in the middle of the groove. Try a couple passes with a good copper brush.

 

[daj]

Driver, thanks for the explanation. I'm still learning to interpret what I'm seeing with the Hawkeye. My cleaning technique may need to change, as you suggest, and that might even cure my major headache of occasional moa fliers.

Getting a load to work consistently in this barrel has been a real pain. It will easily stay in the F-Class center,0.5moa) for eight or so shots then toss in a flier or two, 1 moa up or down.

By way of comparison, my .308 switch barrel is consistency itself, and it's a forged factory tube. Varget is used in both, and the same cleaning regime, but the bore of the .308 has no fouling at all.

I've also slugged the 6.5 bore and it is spot-on 0.264",+/- 0.25 thou) with no detectable tight or loose spots.

If this is just a cleaning problem, I will be one very happy shooter.

daj