AR-10 problem, could use some advise

[esaabye]

I took out a DPMS in 308 today to Pueblo Tac. It was running fine thru 2 stages then on a mag change it became a single fire. It would eject but not strip one off the mag. At the same time the either my aim went to shit or it got loose. I was calling shots center and hitting all around. I swapped mags but no change.


any suggestions where to start troubleshooting?

[Kaiser.Shooter]

That's why I found a few pieces of 308 brass while cleaning the range after our squad shot and was wondering who is shooting a 308 gun. It was a fun match today.
I'd say your rifle is either under- or overgassed, you can check your gas block and tube, buffer spring, sometimes lube the bcg helps too.
Hope more knowledgeable guys will chime in too.

[Lars]

I hade the same thing happen with my 6.5 and it was a lube issue. I lubed the hell out of the BCG and it cured the problem of not feeding.

[Great-Kazoo]

Loose gas block, bolt carrier key, possible gas rings.

[esaabye]

If you factor in the accuracy change that happened when the gas system stopped working I think the gas block is a good place to start. I don't think any bcg issues would impact accuracy. I'll tear it down and start looking.

[Great-Kazoo]

If you factor in the accuracy change that happened when the gas system stopped working I think the gas block is a good place to start. I don't think any bcg issues would impact accuracy. I'll tear it down and start looking.


First place i'd look. BUT.........a loose gas key can cause similar issues. Not as pronounced, still something to check while you're at it.

[SA Friday]

Sounds like carbon build-up and a shitty buffer spring. That's where I would start.

I suspect Accuracy may be a separate issue.

[gta_spec]

Yes, it does sound like multiple issues. Make sure your using DPMS or ASC mags, as PMAG present the head of round .040" lower than required in a LR308 and can cause ftfs or non stripping, IF the carrier is moving back far enough.

[Kaiser.Shooter]

Did you find out what it was and fixed it?

If you factor in the accuracy change that happened when the gas system stopped working I think the gas block is a good place to start. I don't think any bcg issues would impact accuracy. I'll tear it down and start looking.

[esaabye]

Not yet, I tore it down and cleaned it, nothing looked loose or particularly dirty. I pulled the gas block and see some blow by but not more then I would expect.

i was putting a new adjustable gas block to match a new tube so hope to get it out next weekend and work through the possibilities.

[Great-Kazoo]

Not yet, I tore it down and cleaned it, nothing looked loose or particularly dirty. I pulled the gas block and see some blow by but not more then I would expect.

i was putting a new adjustable gas block to match a new tube so hope to get it out next weekend and work through the possibilities.


One mistake i see, a lot. People install the gas block up to the shoulder of the bbl. That's where the hand guard retainer sits. When removed for a float tube they forget that retainer thickness, .025 average. Putting the block flush with the shoulder, not accounting for that space closes off some of the gas flow. That amount can and will (sometimes) cause issues.

[ray1970]

One mistake i see, a lot. People install the gas block up to the shoulder of the bbl. That's where the hand guard retainer sits. When removed for a float tube they forget that retainer thickness, .025 average. Putting the block flush with the shoulder, not accounting for that space closes off some of the gas flow. That amount can and will (sometimes) cause issues.

I've found through measuring that putting the block against the shoulder usually doesn't present an issue. Since the gas port in the barrel is quite a bit smaller than the port in the block there's quite a bit of wiggle room before misalignment realize becomes an issue.

[esaabye]

The rifle is a DPMS 3g1 factory config. I did not see any issues when I pulled the gas block. As for the accuracy issue, I understand that is an easy one to assume is the shooters fault but for the record I won the match with my 223 rifle.

[SA Friday]

The rifle is a DPMS 3g1 factory config. I did not see any issues when I pulled the gas block. As for the accuracy issue, I understand that is an easy one to assume is the shooters fault but for the record I won the match with my 223 rifle.
Aluminum gas block, right? When you pulled it, did you see any scoring or oblation? I have seen aluminum gas blocks oblate from the gas pretty bad and leave particles in the barrel through the gas port. If there is scoring, this is probably your problem.