I think I have a gas problem...

[ShawnZR-1]

Yeah, probably that gas too but in this case, I'm referring to my LAR-308. It's an internally stock factory DPMS.

Yesterday, I was able to get through a 20 round mag with no problems but after that, with the same rounds, I couldn't get 3 in a row off. Some were stove pipes, some were FTF, some didn't even eject from the chamber (jammed another round behind it).

I tried different magazines, then went to different rounds (CBC, ZQI, and even Norma .308 match). No difference overall. I put 1 round in the mag and squeezed it off, and the bolt did not lock back (tried that 3 times in a row). If I charged it normally on an empty mag, the bolt would lock back.

I did some searching and there are a few things it could be but I don't want to just start replacing things without knowing for sure. One of the most obvious things is to make sure the gas block is aligned correctly but I have no idea how to check that.

I'm willing to pay someone to troubleshoot this (as long as they know what they're doing) to make it reliable and more fun to shoot! Or, I am VERY willing to shadow someone and be taught! I love learning! Of course, I'll still pay

 

[ShawnZR-1]

Anyone have any input? Beuler?

 

[mikeyE]

When you put one round in the mag did it eject as it should?

 

[ShawnZR-1]

Yes, it did eject, though compared to my AR15, it didn't spit the shell quite as far.

 

[ASH556]

If the bolt is locking on an empty mag reliably then you have enough gas. Your initial post is a little confusion in that regard as to whether it did or did not. If not reliably locking back, there are multiple things it could be. The thing is, you only want to change one variable at a time so you know what the fix is and don't create another problem in the process. Is this the first time you've fired the gun? If not, what changed from the last time it worked. If so, send it back to DPMS. That's why they have a warranty.

Beyond that, if you're not getting lock back, then here are some things to look at for starters:
Enough lube? Wetter is better and oil is not lube.
Gas rings good?
Gas block and tube installation and alignment good?
Gas key still tight on carrier?
Chamber clean?

 

[ShawnZR-1]

The bolt does not lock back reliably. That's why I am thinking it is undergassed.

The gun has never been reliable. I've focused my attention on the bolt because I thought it was stiff. It's been soaked and cleaned a few times. It has a good coating of remoil throughout. It's almost as if it gets the slightest bit dirty, it stops cycling reliably.

I thought it just needed to be broken in so I was going to go a few times with it before throwing my hands up. Hands are up now. After struggling to get 200 rounds through it, I've gotten to this point.

I'll check all of the suggestions but like I said, I don't know how to check to see if the gas block is aligned correctly.

Thanks for your assistance!

 

[ASH556]

Rem Oil is not a suitable lube. You need CLP, Slip 2000, or heck, even try some Mobil 1 and make it wet. I've turned many a malfunctioning AR into a working one because it was too dry.

 

[timbgtm]

Any marks on the brass? Try hand cycling a mag through to make sure rounds are feeding reliable with out hitting feed ramps.

 

[ShawnZR-1]

Any marks on the brass? Try hand cycling a mag through to make sure rounds are feeding reliable with out hitting feed ramps.

A couple of the cases were dented from the bolt jamming it against the round that was not ejected. None of the rims had any weird markings on them where it may be too difficult to extract. The ones that didn't even extract from the chamber were easy enough to get out, just dropped the mag, fully cycled the bolt and then cycled it again. Spent casing came right out.

 

[timbgtm]

You can do the blow in barrel while keeping a finger on the gas tube to make sure there's no obstruction in the barrel hole, if the air goes through easily it could be over based, if not under gased.