AR15 barrel question

[Keith Glasscock]

I've purchased a complete upper for my AR. My intent was to have a multi-purpose rifle that shoots MOA or better out to 500 yards.

Load development has not gone well. I have had more and more flyers recently. The barrel has 175 rounds through it - all slow-fire while I've been attempting to develop loads. I can't get anything at 100 yards (with flags, bag rider, whole works) that I would call a group.

Out comes the borescope and the barrel appears to be a nicely lapped stainless barrel. The fouling is easily removed with solvent. The only thing I see is that the gas port is drilled right in the middle of a land and that land has broken off for ~.040" past the hole. The copper built up on that spot looks thick, but I haven't been able to remove it with solvent.


I did borescope the barrel after the first 50 rounds, and I didn't see a missing chunk.

Question:

Is a broken off land possibly causing the flyers? If so, do you think that this is a customer risk item, or something that the barrel maker should be contacted about?

Thanks,
Keith

 

[mac86951]

Doubtful, but possible. Check that barrel nut isn't loose, and check that gas block is well seated. I'm assuming you have a free floated foreend? Finally, make sure the gas tube is centered and not touching anything like the barrel nut or upper receiver where it enters the upper. Adjust gas block accordingly to "free-float" the gas tube.

Mac

 

[Keith Glasscock]

If it makes any difference, The barrel is one of the stainless barrels that Rock River sells.

Forend is free-floated. The gas tube appears to be clear. I guarantee that the barrel nut isn't loose because the forend is mounted to it. and it doesn't wiggle. Even with known good loads, it doesn't shoot very well. I've been up and down the ladder multiple times with different bullets. Occasionally, I get a group that runs right at 1", but more times than not, I get 2+"

I swapped out the scope today just to check that. No improvement.

 

[Keith Glasscock]

Cell phone picture through borescope added.

 

[rayjay]

I think you have found your problem. It would be interesting to slug the bbl with a lead slug. I bet it hangs up big time right at the gas port. You could even pull the bullet from a 22lr match cartridge, expand the slug a tiny bit by judicious use of a center punch or similar tool and then push it down the bore from the chamber end.

I have absolutely no experience with gas port sizes but that one seems large.

 

[akajun]

I don't think the gas port is your problem , a well shot out barrel will have a gas port tail eroded from shooting much bigger than that. I had one with 7500 rds on it when it finally gave up the ghost, had a gas port tail about 1" long.
What ammo are you shooting and what is your barrel twist ?

 

[Jeff A]

Do you have the barrel installed with Loc-Tite on the barrel extension? What is the barrel nut torque?

 

[Keith Glasscock]

Do you have the barrel installed with Loc-Tite on the barrel extension? What is the barrel nut torque?

I didn't build this one. Rock River did.

 

[Keith Glasscock]

8 twist - handloads only. 77 Nosler CC, 75 Hornary HPBT, 50 Vmax, 52 SMK.

My question is specifically if this item is a no-go for accuracy. I don't want to putter around messing with it if the barrel isn't going to shoot.

 

[Keith Glasscock]

I have absolutely no experience with gas port sizes but that one seems large.

I don't know the specs either, but I know how to find out. What I do know is that this thing is over-gassed. Even with a heavy buffer, the brass hits the deflector so hard it dents the side of the case.

 

[akajun]

Try 77 noslers / smk's, / bergers/ hornadys with 24 grains of rl 15 or varget loaded to mag length
If that don't shoot under 1" call rock river

 

[Rtheurer]

Good Picture. That actually is very common. In actual testing it was found that a Port in the land or the goove or even partially half and half had no affect on accuracy.
I had a Bartlein Barrel that was looking like it was going to be a hammer, the steel had an Inclusion right on the edge of the port, at around 250 rounds it popped loose and left a large crater and worse yet a jagged edge that actually would strip the Jacket thin there,on a thick jacketed Sierra Match King 77gr bullet. Had bullet blow up after bullet blow up. Had to take it off and put a new one on.
Call Rock River and send the picture. They will make it right. I have had good luck with them. Should be shooting sub MOA out the gate.

 

[Dusty Stevens]

I would think that one would be better than the other 99% that are halfway on a land. I bet its just a bad barrel and they probably wont touch it because its within their specs. Call compass lake and get a krieger on the way. I couldnt be happier with mine.