Gunsmithing DPMS 308 gas issues?

[RidgeRebel]

Somebody posted a similar post on the rifle forum but I have the same issue. I was out shooting my DPMS 308 LR today it is an 18in barrel. I've shot less than 100 rounds through it and I bought it new. It has shot great until today. I shot about 10 rounds and then it started short stroking and jamming up on every round. It was about 105 degrees out so I'm sure it was hot. But I was shooting slow so it wasn't extremely hot. When I got home I striped the rifle completely down including the gas block and cleaned everything completely and oiled everything. Then reassembled it and check it for mag issues. Everything looks good so I think its got to be a gas issue? I have not shot it since I cleaned it. Any thoughts from the AR gurus? What can I check/fix? Thanks for any help you may offer.

 

[our gang]

Re: DPMS 308 gas issues?

I'd call DPMS. I have a 260 & 300 SAUM LR and a 308 16" TAC and none have ever had a malfunction. (except when I tried to use Berger VLDs in the 260). I would suspect the ammo and also blast out the gas tube with brake cleaner (keep it off any non metal parts!!!!!

 

[Casey Simpson]

Re: DPMS 308 gas issues?

We're assuming you fired factory ammo, but if you fired handloaded ammo verify its AR compatability; see www.Zediker.com and The Competitive AR by Glenn Zediker.
Your issue sounds like a mag lip issue, but while you're thinking about it, do these tricks:

polish the bolt face and lug faces by chucking in a drill and hold the face against 400 grit oiled sandpaper and finish with micro fiber and Flitz.

polish the chamber with a bore mop and flitz using a rod in a drill.

get the parkerized finish off the carrier and polish it.

replace the buffer spring with a CS spring from Superior Shooting Systems. Get the trigger and hammer springs while you're at, and the Final Finish, and the Carrier Weight System.

Lubricate the the lugs with Slide Glide or other good grease.
Lubricate the bolt and carrier with something good like Mobil 1 motor oil. (Oil doesn't need to smell pretty to be good).

Clean, lubricate, shoot, clean, lubricate.

Get a good trigger and fix the magazine lips; that gun shoots good.

 

[Brain]

Re: DPMS 308 gas issues?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Casey Simpson</div><div class="ubbcode-body"> but while you're thinking about it, do these tricks:
<span style="color: #FF0000">
polish the bolt face and lug faces by chucking in a drill and hold the face against 400 grit oiled sandpaper and finish with micro fiber and Flitz.

polish the chamber with a bore mop and flitz using a rod in a drill.

get the parkerized finish off the carrier and polish it.

replace the buffer spring with a CS spring from Superior Shooting Systems. Get the trigger and hammer springs while you're at, and the Final Finish, and the Carrier Weight System.</span></div></div>
Don't do any of the above "tricks" to your rifle. It will run fine without modification/abuse.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Casey Simpson</div><div class="ubbcode-body">
Lubricate the the lugs with Slide Glide or other good grease.
Lubricate the bolt and carrier with something good like Mobil 1 motor oil. (Oil doesn't need to smell pretty to be good).

Clean, lubricate, shoot, clean, lubricate.

Get a good trigger and fix the magazine lips; that gun shoots good. </div></div>
Do lube necessary points on the rifle.


Unless hand loads were being used which were improperly sized/loaded for use in this platform, I'm suspecting mag issues.

 

[wordisbawn2008]

Re: DPMS 308 gas issues?

did you put an aftermarket stock on the rifle? i heard of a case where a guy put an aftermarket stock on an ar-10 but used the factory stock screw and it was too long, ended up interfering with the buffer spring causing something similar to what you've stated.

 

[Pat M]

Re: DPMS 308 gas issues?

!!! First check to see if the allen screws holding the gas block are loose, my buddy had his loosen up on his DPMS 308

 

[Casey Simpson]

Re: DPMS 308 gas issues?

Brain, please see. e.g.;
THE COMPETITIVE AR, by Glenn Zediker

Define "fine". I'm suggesting how to get it to run superbly. Merely "fine" is what't got it jamming. Unless you mean fine as in fine wine or china, or fine as in adequate or okay.

 

[RidgeRebel]

Re: DPMS 308 gas issues?

As a matter a fact I did change the stock to an ACE but I didn't think much of it since the buffer tube is still factory. But I will change the stock back to the factory A2 stock and see if that solves the problem. Thanks for the help guys.

 

[Strangedays]

Re: DPMS 308 gas issues?

What ammo were you shooting? I have had a bad box of ammo do that but switched the ammo and everything ran great!

 

[mattsnuked]

Re: DPMS 308 gas issues?

My DPMS LR308 would not run with factory mags. I bought the C Product mags and it now works flawlessly.

There is a known DPMS mag issue with certain lots.

 

[cockcroft]

Re: DPMS 308 gas issues?

Great! I just bought 10 mags for my LR308, hope I didn't get the bad ones.

 

[our gang]

Re: DPMS 308 gas issues?

Almost all I shoot in my ARs are reloads. If you use appropriate powders and bullets they work fine. I don't even FL size, because when that bolt slams home it always chambers the 223, 260, 308 or 300 SAUM. I toss the cases after 5 reloads anyway.
TAC in the 223, 4350 in the 260, BL C or Varget in the 308 and W760 in the SAUM. KISS works! and don't try Berger bullets!

 

[Bronco]

Re: DPMS 308 gas issues?

Check the buffer and make sure it is pinned, and if not the bumper plug can work lose and cause the short stroking. Check gas key to make sure it is tight. Look at the gas rings to confirm gaps are not lined up. Leaks around gas block? And the aforementioned mags, look brass over to see any drag marks etc.

 

[Brain]

Re: DPMS 308 gas issues?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mr. Humble</div><div class="ubbcode-body">and don't try Berger bullets! </div></div>

Care to elaborate or link to some substantive data to support why they will cause malfunctions?

 

[RidgeRebel]

Re: DPMS 308 gas issues?

I was shooting Fed GMM 168 grn factory when it first started. It damages 3 rounds and I switched to some handloads with the same results. I don't think it's an ammo issue. I will have to tear it back down and check the gas rings and gas key. There didn't appear to be any leakage from the gas block. What do you mean about the buffer being pinned? Thanks for all the replies guys.

 

[our gang]

Re: DPMS 308 gas issues?

My substantive data is that when I tried the 140 VLD in my DPMS AR 260LR they:
Had to be seated in so far (to fit the magazine) that there was a space between the bullet and the neck.
They would "catch" on what I would call the feed ramp, due to their shape

Great bullets for paper and steel in my 6.5x55s (long actions).

The Noraa, SMK & Amax 140s worked perfectly in the AR. As does the 130 TSX that also kills Antelope right now.

 

[Brain]

Re: DPMS 308 gas issues?

Your advice, based on experience in a DPMS 260, is irrelevant as the rifle with function issues here is a .308.

Perhaps you should be more specific instead of issuing a blanket statement like "don't try Berger bullets" in the future. Then, make sure your advice has relevancy to the problem at hand.

 

[okiefired]

Re: DPMS 308 gas issues?

If its short stroking its highly unlikely its a feed ramp issue. The only way I can think it would be mag related is if the mag lips are bent so severly they're draging on the carrier or letting the next round do the same. Try another mag to make sure. Since you've cleaned it well, make sure the carrier and bolt are lubed properly and let us know how she runs then. Or, just trade it for an Armalite

. Sorry, had to say it, just bustin your chops a bit. It'll run after you get this little problem worked out.

okie

 

[Bronco]

Re: DPMS 308 gas issues?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: elksniper</div><div class="ubbcode-body"> What do you mean about the buffer being pinned? </div></div>

Most buffers have a pin in the end with the bumper that hits the back of the buffer tube. If it isn't pinned the bumper can work out far enough so the bolt can't make it back to lock open or cycle another round. Guess how I know this.

 

[RidgeRebel]

Re: DPMS 308 gas issues?

Went out for a re-shoot after a thurough cleaning, inspection of all parts and stock swap back to the original stock. She shoots great. I don't know which part caused the problem but I gues it doen't matter now. Thanks again for all the help guys.

 

[Casey Simpson]

Re: DPMS 308 gas issues?

It matters; keep an AR clean and properly and adequately lubricated, i.e.; film of good oil on the carrier top careful to not have too much that it runs onto your ammo which hopefully makes it to the chamber where oil is not wanted.
1 Oil the hammer and trigger pins, and their springs.
2 Oil the extractor and ejector springs.
3 Grease the bolt lugs, sear.
After firing, remove all lube and crud, from these parts, carefully and properly clean the bore, and re-lubricate the weapon with oil until ready to fire again.
Clean and maintain the magazines.
Before firing again, repeat 1,2,3.

 

[DRAM40A1]

Re: DPMS 308 gas issues?

I ran FGMM in an 18 inch DPMS and the shavings from the ejector swipes would stick the ejector and cause the same issue you were having. Black Hills or reload with Winchester and you will see a big difference. I now have a GAP AR10 and Federal does the same shit in it!!!!No more Federal brass for me.LOL.