AR issue.

[DRob]

AR gurus......Help please.

One of our AR varminters in .204 started denting the lower right side of the cases. The dent runs around the case from about 3 to 8 o'clock. I think it is happening when the round is chambered because fired cases are not dented just scratched or marked in the same spot. It happened with several magazines. Here's a bad photo but it does show the dent. Thanks.

 

[rgarner74]

This just happen once, every 10 to 15 rounds?

 

[DRob]

More often

This just happen once, every 10 to 15 rounds?

More like every 6-8 rds.

 

[sloughfoot]

Severe danger. I would want to check out the rifle. Guessing on the internet is not good enough.

 

[EODThree]

It looks to me like the projectile is being forced into the case mouth and then the mouth is impacting the rear of the chamber.

What kind of crimp are you using?

Are you getting erratic groups?

 

[DRob]

No crimp

It looks to me like the projectile is being forced into the case mouth and then the mouth is impacting the rear of the chamber.

What kind of crimp are you using?

Are you getting erratic groups?

I'm not crimping the rounds. The OAL doesn't change when the round hangs up. In almost every case, the round fully chambers unless I ease it in by slowly lowering the bolt. The rifle has been very accurate but hadn't been shot for a while when this started happening. Last time I shot it at the range, it was shooting well under 1 MOA.

 

[DRob]

New findings

Well, while tinkering with the gun, I found a couple of things. One: Rounds fed from the right side of the magazine get dented while rounds fed from the left side usually only get scraped. Two: There is a small amount of interference when the gas tube enters the carrier key. When operated by hand it actually moves the bolt slightly downward within the receiver. I find it hard to believe that could be the problem but my other ARs don't do it.

 

[IndyGunworks]

If the bolt is being moved by the gas tube, that needs to be remedied first. Once that is fixed then see if you still have this issue.

might also try extra power mag springs to help get some additional upward lift on the bullets in the mag.

 

[IndyGunworks]

also,if this is a gun you build, or was built by someone (not factory) then check to see if its a rifle style barrel extension in a carbine reciever w/ the feed ramps cut into the reciever. sometimes that will cause a bullet to hang up when it hits the reciever feed ramp then has to force its way over the extention in order to get the the barrel extensions ramp.

 

[DRob]

Built????

I don't know who built it. I bought it used at a gun show several years ago. It has shot like a champ until last month. It had not been shot for a while but I cleaned it before we went...just because. I think the upper needs to be disassembled but I don't have the tools and I've never done one. Been looking around the net for assembly/disassembly info which is out there. The issue with disassembling it is that it has an adjustable gas tube. The adjustment valve extends through the top of the floated forearm.

PM sent IGW.