Carbon Ring ID help

[dixiecricket]

Folks,
I could use help on identifying if this is a hard carbon ring or not. its a Proof CF Pre-fit .308 barrel that has never really shot up to expectations with normal high BC boattail bullets. I borrowed a bore scope before trying out the Litz JB bore paste cleaning and a chamber neck scrubbing with a fresh .338cal bore brush in a drill and I wanted to document the changes if any. probably 400-500rnds on this barrel. I did clean around 200rnds with copper solvent and it was super easy to clean.

photos taken from the muzzle end of the end of the chamber neck to throat junction with a case partially inserted and then fully inserted. there is a gap what i would guess is 0.020" to 0.030" from the end of the case mouth to the darkest ring. all of the rounds shot thru this barrel were M118LR or reloads with M118LR 1x fired brass and CFE223 or some Varget. The barrel does shoot well (1moa 10 shot groups) with flat based 135gr Sierra Varminters and a full case of CFE223.

I cannot get M118LR or any of the Berger and Sierra bullets I have on hand to group at an MOA or better for 10shot groups, which is my basic expectation. ****I'm not here to bash on Proof, this is about the carbon ring*****

 

[dixiecricket]

First look after spinning a chamber brush in there for about 15sec. Still a dark black ring.

 

[DShortt]

Yes, there is a hard carbon ring there. That's the black line you are seeing. You'll have to use the JB Bore paste, a worn bore brush and a patch wrapped around the bore brush to get it out. Based on my experience.

Now, do I think that carbon ring is causing accuracy issues?

No, in my opinion that's not the cause. Particularly since a different bullet/load shoots well.

You might want to check the velocity and see where it's at.

 

[jelenko]

carbon ring is causing accuracy issues?

No, in my opinion that's not the cause. Particularly since a different bullet/load shoots well.

This especially. Something other than the carbon ring is causing issues.

How comfortable are you that with a tack driving rifle and tuned ammo you would shoot consistent sub moa groups?

 

[dixiecricket]

I am very confident that i can shoot sub-moa with a rifle capable of delivering that accuracy.

I considered that im having some non-ammo/barrel shooting issue, but im able to hold MOA or better with 130gr TTSX @3080fps 5 shot groups and 0.7-0.9moa 135gr Varminters at 3120fps 10shot groups. 175smk, 180AB, 185Jugg, 155TMK, 168 Ber VLD, and 190smk are all 1.2-1.6 moa.

 

[DShortt]

I am very confident that i can shoot sub-moa with a rifle capable of delivering that accuracy.

I considered that im having some non-ammo/barrel shooting issue, but im able to hold MOA or better with 130gr TTSX @3080fps 5 shot groups and 0.7-0.9moa 135gr Varminters at 3120fps 10shot groups. 175smk, 180AB, 185Jugg, 155TMK, 168 Ber VLD, and 190smk are all 1.2-1.6 moa.

OK, so verify the rate of twist.

Maybe this barrel is a 1 in 12 or less. (?)

 

[dixiecricket]

100% a 10T unless its is miss laser-engraved.

 

[DShortt]

100% a 10T unless its is miss laser-engraved.

Well, if it were mine I'd slug it and check for consistency.

Not a task for the faint of heart, but completely do-able if one is careful and uses the correct techniques.

And it might be mis-marked. Mistakes happen.

That's why I check everything.