6.5 grendel poor accuracy, bad barrel?

[brasscollector]

It is an 18" stainless barrel, 8" twist, A2 flash hider and had zero rounds down the tube when I bought it. Right from the get-go the accuracy was bad, 2-2.5" @ 50yds, 4-5" @ 100yds. Patterning is weird also, 2 shots nearly touching then the next one is 4" high-left and then 2 more nearly touching but 3" low left. I tried 120 noslers, 120 sierras, 100 amax/eldm and several different powders and charge weights. I also ran a 20rnd box of Hornady Black through it. I removed the flash hider, tried an accu-wedge (HA), different scopes, magpul locking stock, copper cleaning and even went through the trouble of loctiting the barrel into the receiver. On Friday I borrowed a borescope from a friend and found some damage to the lands. Approximately 2-3" back from the muzzle there is maybe 1/4" of damage to 4/5 of the 6 lands. Is this enough to cause the lack of accuracy I'm describing?

[ed308]

I would think damage to the lands close to muzzle would be a problem. I would suspect some of the bullets are damaged as they pass over the damage area. Is it possible you could speak to the manufacturer and exchange the barrel? Either way, I'd be looking for another barrel. If purchased used, I'd talk to the person you purchased it from. Doubtful it had zero rounds, unless they bore scoped it and saw the damage.

[brasscollector]

You're correct on the barrel now that I think of it, it could have had rounds through it. The upper was new, unfired but that is no guarantee the barrel hadn't been shot before. I bought it from a friend who has assembled a few I own. He said he would send me a replacement or even swap me out to 6.8 or x39, etc so I'm not worried. He thought it sounded like damage from a tool used to cut the muzzle? I'm just hoping a new barrel cures the issue.

[CarJunkieLS1]

That damage definitely isn't helping accuracy. I agree with your friend that it was damaged during the making of your barrel. I have no doubt that a different barrel will solve your problem.

[44caliberkid]

Did you clean the barrel first, when it was new, before you shot it? That is always my first move and every one is filthy, often finding steel chips from machining on the first patch. I never fire a new to me weapon without cleaning it first.

[brasscollector]

I did clean it prior to shooting it for the 1st time which is usual practice for me also. The first few times I cleaned it (likely @ 50rnds, 100rnds and 150rnds) the patches indicated copper. The last few times I've cleaned it the patches are just gray/black, no blue-green coloring at all. I imagine I burnished the copper-cutting rough spot out.

[doofus47]

I don't like the damaged lands, but how are your scopes mounted? Different scopes/same rings? Different scopes/different rings?

[brasscollector]

First scope was a cheap 3-9 that I keep around because it always works. Second scope was a new Vortex crossfire and both were mounted in a (Redfield?) cantilever mount which is clamped only to the receiver. I've learned my lesson about optics partially mounted to the heat shield.

[T. O'Heir]

"...Patterning is weird..." That's not caused by damage to the rifling. Sporadic groups are usually a bedding issue. You still need to send the barrel back though. A brand new barrel should have a warrantee for that kind of thing. Isn't something you could have caused. Falls under manufacturing defect.

[Double Naught Spy]

What a bizarre story.

Your 'friend' sold you a piece of junk. Get rid of it. Take the offer of a replacement.

[rickyrick]

If you gave no other information than the description of the groups, I'd say that you have a scope mount loose.

But, all the other information does point to the barrel. Besides the bore damage, aggressive tightening of the flash hider could've tweaked the end of the barrel.

Advice for the future:
If you want Frankensteined uppers, learn how to do it properly yourself. ARs are easy... I've spent more time trying to get a vacuum filter back in than assembling uppers.

I'm curious as to how many times this barrel has been passed around.

[Mobuck]

A "bad" barrel usually throws random hits into a large group rather than 2 hits here and 2-3 hits somewhere else. Or the groups "wander" in a fairly repeatable fashion as the barrel heats.

[doofus47]

Did you take 2 shots, adjust your scope and then take 2 more shots, etc?
Maybe the adjustments to your scope is having issues.

I'm with the other guys that you should swap the barrel, if it's an option

[brasscollector]

I did chase the adjustment around a couple times but usually when I'm having accuracy issues I get the scope pretty close and leave it. I sent the bad barrel back and should have a replacement next week.