Gunsmithing Help with a possible chamber problem

[D46Infinity]

I am having a problem with a rifle. First it won’t group to save my life. It is a factory made production barrel from a known rifle company. I have fired it and had others shoot it with the same results.

The complete rifle was assembled by me and I really just need a little help confirming what I believe is the problem.
The rifle is large frame gasser in 6.5 creedmoor.

Initially the rifle would not run, so I adjusted the position of the gas block which is also from the same company and for which the barrel was factory dimpled for and that fixed the cycling.

Now the rifle will not print a decent group. It is shooting a 1.5” group at best with the companies so called ultra precision barrel.

Ammo is hornady factory140 and 147 eldm.

So from the very beginning the brass has been coming out with rings just below the shoulder and continue down just above half way on the brass. They are concentric rings around the brass.

The chamber also has the rings from what I can see inside. I can’t get very good pictures of the chamber, but I have pics of the fired brass.

I think the chamber was cut incorrectly.

I did get in touch with the manufacturer and it is on its way back to them for inspection. So far their customer service has been good. When I originally called them about the cycling issues and accuracy issue, their response was the rifle was not assembled correctly and there must be anti sieze between the barrel extension and upper receiver. I have never heard of this being a problem, but I went ahead a disassembled the upper and confirmed no anti sieze was present there as I did use it on the barrel nut.

Let me know what your think.

 

[GH41]

Tell us about the rest of the rifle and your experience shooting an AR. Assuming the 1 1/2" groups are at 100. I would say that's a fair group if you are a novice shooter, shooting factory ammo especially if the trigger is shitty.

 

[supercorndogs]

Tell us about the rest of the rifle and your experience shooting an AR. Assuming the 1 1/2" groups are at 100. I would say that's a fair group if you are a novice shooter, shooting factory ammo especially if the trigger is shitty.

Especially with a big frame AR.

 

[Jarridmoore]

Let’s see the groups

 

[D46Infinity]

I don’t really consider myself a novice. I have a few other large frame rifles including a gap10 and I’m really consistent with it. Usually printing .5 to .7 moa with it.
Here is one of my gap 10 groups with the same hornady factory eldm 140 ammo.


That is why I had a friend of mine also shoot it and he is just as consistent as I am and probably better. His group was right at 1.5”

The trigger is a Larue MBT, it’s not all that bad for a 2 stage this one actually breaks really nice.

 

[D46Infinity]

Here are some pictures of the groups this rifle is getting. Both mine and my buddy shit these.

 

[GH41]

A couple of stupid things to check... Is there anything mounted on the handguard with a screw anywhere close to contacting the gas block? Can you rule out the scope? Maybe take the scope and mount off of the GAP and try it. Don't bother with changing the zero if it's on paper just shoot for groups.

 

[Bandit31]

Looks definitely like tool marks in the chamber to me. Might explain the cycling problems but it should still shoot okay, at least a rifle of mine that had really bad tool marks in the chamber did.

Being that it's already on its way back from the manufacturer, I'd hope they replace it.

 

[D46Infinity]

Scope is a Scmidt US 3-20. I pulled it off my gap. I tried another Schmidt 5-25 with the same results.

They received it today so I’m just waiting, I’m sure it will take a few days before I hear anything. Probably next week at the earliest.