AR-10 double grouping?

[Adam in WI]

I know it's only 2 groups, but they're similar shaped, at least to my thinking. These are 2 five shot groups fired today with an Aero Precision M5 with a no- name 6.5 CM barrel. First 5 are the higher ones shot at 100 yards, next five are lower and were fired at 200 yards. They appear to be similar shaped, seeming to string a little diagonally down/ right.



Do you think this is a shooter issue (I'm not an expert in ARs by any means), or is this a barrel/receiver fit problem? Or is it just a cheap azz barrel issue? This barrel is probably going to be pulled eventually, but I'd like to know some possible causes for what I'm seeing.

Thanks folks

 

[Coyotefurharvester]

Barrel nut torque issue, if you made a scope adjustment between groups.

 

[Adam in WI]

No adjustments done. You think I should loc-tite the extension and retorque?

 

[msalm]

No adjustments done. You think I should loc-tite the extension and retorque?

That and face the receiver for a perfectly flat/perpendicular face for the barrel extension to torque on. If you want to that, bring the stripped upper over and we’ll do it in 5 minutes or so. I made a mandrel for the lathe for each 15 and 10’s, quick easy operation.

 

[Coyotefurharvester]

Yes,Yes. Make sure the barrel nut has clearance. Don't twist the rifle(clockwise) when breaking the shot.

 

[Dimner]

If you use loctite on the extension, make sure it's the bearing retention version. Im pretty sure its It's what BCM suggest to use. Loctite 620. It will span very small gaps in the fit between barrel extension and the mating surface in the receiver. However, this treatment means its much harder to swap barrels. If you are a competitor and swap barrels after a certain round count, and shoot high volume, you may want to find a stripped upper with better tolerances.

 

[Adam in WI]

I made a mandrel for the lathe for each 15 and 10’s, quick easy operation.

I had a lap bar made for the 15s. Might see if I can get one done for the 10s also.

 

[msalm]

That’s tedious, way easier with carbide single point pass on the lathe

 

[Klong]

Shoot a few more groups at 200 yards. Shoot 10 shots. I suggest 10 shots magazine fed and 5 or 10 shots single fed. You will need to see what those tell you. Shoot it with a loose grip and not a death grip on the rifle Maybe change seating depth. Are you using front and rear bag or a bipod?
!

 

[Dimner]

Also, something worth testing is to single shoot your next groups. Meaning, do not mag feed. Take that part out of the equation. So you skip the feed ramps and everything. A burr or defect on a feed ramp vs the other feed ramp can cause issues with double grouping. Not sure if it's as prevalent with 6.5cm, but worth isolating that variable.

 

[jwink]

My AR-15 did the same thing once, I torqued the barrel nut and problem went away.

 

[whatsupdoc]

Lots of possibilities, the one thing I want to mention is that different holds on AR's
will cause the point of impact to change.


Try again at 100 yards and concentrate on how you hold the rifle, make sure you are pulling the rifle into your shoulder. If you are trying to shoot a group and the rifle feels weird stop
and reset.

 

[mac86951]

Is the barrel nut touching the gas tube?

 

[Adam in WI]

Thanks for the ideas folks. I did some checking around last night. I didn't find anything noteworthy in terms of stuff touching or binding on the barrel, receiver, or gas tube. The screws clamping the handguard to the barrel nut weren't what I would call tight, but with hand pressure I was unable to move it.

Matt; my other barrel is a month or two out. I might just take you up on having the receiver face trued.

For now I'll try some of the single load suggestions and maybe check the barrel nut torque. I've often read these rifles require a good driver; all shots I've taken have felt good with no real tenancy for the rifle to roll or jump. Recoil is surprisingly minimal, and the way it ejects suggests the gas is about right. As mentioned before, I'll be swapping barrels not too long from now. I just don't want to be surprised if it shows the same pattern.

 

[mac86951]

Thanks for the ideas folks. I did some checking around last night. I didn't find anything noteworthy in terms of stuff touching or binding on the barrel, receiver, or gas tube. The screws clamping the handguard to the barrel nut weren't what I would call tight, but with hand pressure I was unable to move it.

Matt; my other barrel is a month or two out. I might just take you up on having the receiver face trued.

For now I'll try some of the single load suggestions and maybe check the barrel nut torque. I've often read these rifles require a good driver; all shots I've taken have felt good with no real tenancy for the rifle to roll or jump. Recoil is surprisingly minimal, and the way it ejects suggests the gas is about right. As mentioned before, I'll be swapping barrels not too long from now. I just don't want to be surprised if it shows the same pattern.

Any information on how it shot, as in sequence? Could the split be due to which side of the mag it's feeding from; IE could one side of the feed ramps need some additional deburring / polishing?

-Mac

 

[Adam in WI]

No, sorry. I don't that much detail.

 

[Ranger188]

I had a scope that's reticle was shifting and did that.
Something to check.

 

[Wildcats]

What bullet and load data?
AR 10 rifles can be very finicky and bolt action load data won't work in a gas gun,specially an AR10
Also barrel is one of the #1 key to AR accuracy..can't go cheap there.

 

[Adam in WI]

What bullet and load data?
AR 10 rifles can be very finicky and bolt action load data won't work in a gas gun,specially an AR10
Also barrel is one of the #1 key to AR accuracy..can't go cheap there.

Virgin starline
WLR
42.0 IMR 4350
130gr Eld-M
2.8"

 

[jxb]

I don't see the problem, just shoot 1/2 as much and you're good to go. Might save some $ on ammo too!


ok ok, appears something is loose either on the gun or in the scope of it goes back and forth consistently.