Update. 11/22/2014 gas port in barrel is .0700 or a #50 drill bit.
WHAT SIZE SHOULD IT BE?
Also, there is .7" gas tube protrusion into the receiver, IS THAT ENOUGH?



Part # on box is RFLR-OC. 16" barrel. LR-308
Been fighting this DPMS LR308 for a several weeks now. 85 rounds of various nato and .308 ammo up to this point.
Most times, It would Shoot 1 round but would not pick up 2nd round, Many FTEject, stovepipe and failure to pickup next round or lock back on empty mag.
Tried about 7 different surplus NATO and .308 ammo brands.
Gas block is aligned correctly and checked. Lubed it until wet.
Had a collapsible buttstock that came on it with the .308 buffer and spring and it would cycle sporadicly in this set up, a few rounds at most.
I put a A1 stock with DPMS .308 buffer and DPMS .308 buffer spring on it and it ran worse.
On a whim, I went and got the buffer spring out of my 5.56 AR and put it in using the .308 buffer.
Sonofabitfch runs fine now.
Put about 65 additional rounds through it after installing the 5.56 buffer spring and it ran without malfunction.
Total round count now @ 150 rounds.

Crazy thought, has anyone had to cut coils on the .308 buffer springs?
I put the .308 buffer spring back in it and locked the bolt open. I may try it one more time.
What size should the gas port be?

EDIT: Small update.
Had the .308 recoil spring locked back for 2 weeks.
Gun worked for about 15 rounds, had a couple ftfeed, 2 ft lock open on last round in the last 15 rounds.
Seems a bit better now with the .308 recoil spring. I think I'll buy another and start cutting coils on one of them.
Had some pretty good groups for rapid fire from the bench at 50 yds.
I'll clean her up, lube it and start cutting coils.

12/16/14
Never did cut more than the original 1 coil and open the gas port.
Been to the range several times and have a total of 250 rounds through it with about a hundred since opening the gas port and has not missed a beat.
A week ago I put Surplus through it at 200 yards got a 11 1/2" group.
Bough some Fed American Eagle 168grn HPBT Match ammo and shot it yesterday, 12/15/2014, Way better.

I posted the following in ammo also.
Well, i shot 20 rounds through my 16" barreled LR308 this afternoon.
2 sets of 5 shot, 3" and 3 1/2" groups @ 200 yards, 2 sets of 100 yd 5 shot groups, one at 1 3/4" other at 2 3/4",
winds crossing gusts 10-25 mph, 50 degrees, from the bench, only the front on a rest.
I RAN to the 100, posted 2 targets, RAN to the 200, posted the targets
and RAN back so my heart was pumping good for the first 10 rounds.
RAN to the 200 and looked at target and RAN back and shot 5 more at 100 and then 5 more at 200.
I'd say it was pretty good considering the wind, I couldn't hold still
because my heart pumping and wind blowing me around.

Edit; 12X Leupold 5 shots at a time magfed from 10 round magpul mag.

On a 16" barrel .308, I don't like the gas port at CLGS.  Too much dwell time, too hard on the gun, too erratic in behavior.  Is it a complete factory gun out of the box you describe?

What magazines are you using?  Do you have different mags available?

Does your carbine look like this?



In my opinion, those carbines are basically good for a donor action. They are from the Randy Luth era, where every corner that could be cut, was.  

For starters, the following parts need to be sh*tcanned:

* Gas block:  If it is aluminum, it will soon start to allow gas leakage if it isn't already.  Get someone that knows what they are doing (good luck), clamp the barrel in a vice, not the upper, remove the flash hider, remove the gas block, and replace it with a steel one. Make sure the ports are aligned-don't assume that the shoulder on the barrel will mate up with the rear of the gas block and all will be fine.  The ports have to align.

* While you're at it, take the silly handguard cap off unless you plan to stick with a heat trapping, accuracy ruining old school carbine handguard set, like those glacier guards.  Consider getting a quality free float tube that is lightweight, and will allow you to hold the gun better.  The Midwest Industries K-Series Free Float KeyMod Handguard Low Profile LR-308 is one option.

* Buttstock (I doubt it would even be accepted on an airsoft forum in a pay it forward giveaway thread, if they have those). Toss it.  

* We need to troubleshoot the operating system more before I can make any other recommendations.  See what a steel gas block will do and take it from there.  These really are project rifle foundations in my opinion and experience, not something one can expect to work well out of the box, given some of the critical component selections on them.

Using PMags10 and DPMS 20's.
That's the gun I started with.
Gun now has steel, lopro 2 set screws gas block, gas ports are aligned as noted above.
Also installed is a Troy TRX.308 EXTREME 13.8" DPMS LOPRO Battlerail handguard.
As noted above, A1 Colt buffer tube and stock and now 5.56 buffer spring with  DPMS .308 buffer.

Mine gagged repeatedly on S african ball, W german ball and some other import I can't remember.   Of course, if we RTFM it says not to use that ammo.   I had more issues with the loaded rounds sticking in the chamber than FTF/FTE.
In the process of troubleshooting, I stripped the bolt and found a burr under the extractor claw.  stoned the burr off and have had no further issues with US made ammo or my handloads.   Just shot some barnes vor-tx, the ones that are not supposed to group well.  Hair over 1" at 100 for 5 shots.   I have the 16" MOE LR 308.

I had extraction problems with my LR-308 as well.  The extractor was made incorrectly, but a replacement one fixed that to an extent.

Next was the chamber, which was very tight for a self-loader.  Whatever reamer they used on my particular anecdotal sample, it would have been more appropriate for a precision bolt gun.  It choked on full-length sized Lapua brass.

Any people wonder why I don't buy factory rifles anymore.  That LR-308 was actually the last factory rifle I can think of that I bought off the shelf...hmmm, it's been 7 years since then.

After you analyze your extractor, check the gas port for diameter.  I'm interested in what it is, unless you Red Loc tited it in place.

Check the gas key that it is tight, staked well, with no leakage coming out of the sides.

I am getting old, forgot to say I also did the "Chamber polish" with flitz and a 20 ga. bore mop.  
Chambers are a funny thing though, they should not  be too smooth.  Tread/polish lightly.  That particular 308 is one of my favorite ones now, although I hated it at first.
I also put a RRA match trigger in it, huge improvement.

I had an LR308 about 3 years back. I also could not get it to run no matter what I did. Dumped it and went back to a 5.56 platform for dependability. It would take a miracle to get me to buy another DPMS again.

Extractor looks fine, gas block is loctited in and no leakage noted.
Gas key bolts are tight and staked. No leakage noted.
BCG slides easily in the upper, gas rings are good and tight.

Like I said above, it runs perfect with a 5.56 buffer spring.
Has anyone cut coils on the .308 buffer spring?

I haven't, but I have heard of it being done.  The appropriate recoil spring and buffer combinations have always worked for me in the AR10, once I got other issues resolved on factory guns.

The one factory rifle that never gave me trouble was the ArmaLite Inc. AR10T.  My two custom GAP AR10's have always run well.  The only time I have had malf's with my .260 Rem were:

* Ejection port door closed on first round-bounced case back into port, causing stove pipe

* Virgin brass not sized before loading in the .260 Rem, as I have a very tight neck in mine

For rifle-length stocks and RE tubes, the standard AR10 buffer (not AR15) and recoil spring seems to work well in the ArmaLite Inc., as well as DPMS guns.

Could you video in HD your rifle firing from the side with a view at the ejection port, so I can see how fast it is cycling.  Slow motion would be great.  If not, what clock position is the brass ejecting/landing at?

EDIT: Small update. Total 30 more rounds fired.
Had the .308 recoil spring locked back in the action for 2 weeks.
Gun worked for about 15 rounds, had a couple ftfeed, 2 ftlock open on last round in the last 15 rounds.
Seems a bit better now with the .308 recoil spring. I think I'll buy another and start cutting coils on one of them.
Had some pretty good groups for rapid fire from the bench at 50 yds.
I'll clean her up, lube it and start cutting coils.

Edit: actually the ftfeed was bolt over round, not cycling far enough back to fully pick up  the next round.

out of curiosity, did you contact DPMS about the issues?    They seem to be pretty good about warranties or fixing issues.

I have a DPMS LRL-308 24" and it is an absolute tack driver.  No issues ever.

A couple things.   I had a friend who had a problem with the buffer spring catching on the rough interior of the buffer tube.  The spring was not sliding in the buffer tube, causing the action to short cycle.  Check the inside surface of your buffer tube.  It should be relatively smooth.  My friends was not smooth.  In fact, it almost looked like it was threaded.  Very strange.  He replaced the tube and was off to the races.  

I personally sent mine back to DPMS for similar issues.  They re-polished the chamber, and sent it back.  It works fine now.  I read on Arfcom that these guns like to run wet.  So I cleaned it well, and went heavy with the M Pro-7.  Again, she runs like a top now.  

I can tell you that mine likes the 20 round P-Mags better than the DPMS 20 rounders.  Go figure.  

Also, the only ammo I've ever shot out mine was either Federal Premium, or my own ammo made with new Lapua brass and match grade components.  I don't run crap through any of my guns.  YMMV  .

I did not contact DPMS since I changed the handguard, gas block and buttstock and buffer tube assembly.
I have an A1 stock with Colt tube, DPMS .308 spring and .308 buffer in the gun.
Receiver extension is smooth and BCG travels full length inside of it.
I've tried about 7 different ammo brands of .308 and 7.62 Nato with essentially the same results.
Also been using PMags and running it "wet".

Sir, your gun is borked. Please send it to me for immediate disposal.

Are you SURE its not a gas issue? Sounds like its not getting enough...

Update at top also. 11/22/2014

gas port in barrel is .0700 or a #50 drill bit.
WHAT SIZE SHOULD IT BE?

Also, there is .7" gas tube protrusion into the receiver, IS THAT ENOUGH?

Opened gas port to .0760 and put it all back to gether and went to the range.
Ran 30 rounds through it and it locked back on empty mags and had NO misfeeds or FTE.

Problem solved, Congrats! Enjoy yer rifle!

Interesting.  On 5.56 CLGS 16" guns, the gas port is typically .068".  On a MLGS 16", they are typically .078".  MLGS 18" is often .076".

Looks like you actually needed a little more gas, especially to run in cold temperatures.  What were the temps on your first range trip, and what were they for this last test?

Earliest range trip temps were probably 80-90' and the last few were 60-70' today was 55' and rain.
Shot about a 2" 10 round group at 50yds with ZQI14 with 12X Leupold scope just shooting off elbows on a table, no chair.
Using the same types of ammo.

Update at bottom of post 1.
She's running good now.

Glad to hear you got her running smooth...Often, on the Gen 1 LR-308's it's a small problem or a combination of
small problems that that lead to the poor functioning of the rifle with FTF, FTE, and so on...

I would also agree that the CLGS does not belong on a high powered .308 class gas gun of the AR series of rifles,
there is just too much bolt velocity, wear and tear, and heat developed by the action of that gas length that leads to
so many problems...

Of course the other problem that plagues the AR-10/LR-308/SR-25 class/series of rifles is the non standardization of
the platform, as it relates to parts and components compatibility...Now some manufacturers are sourcing some parts
from China which will only make things worse...

Lets hope the new DPMS G2 platform of AR rifles sets a higher standard of quality and performance over the original
LR-308 series for DPMS and leads to more of a standardization in the near future for the large frame AR's...

Most of the problems are with the min chamber........I used the reloads from my other 308's and were getting rounds stuck in the chamber !!!
Also all surplus ammo would jam. Got out my case guage and found out only min sized chamber loads would work.
Next went into chamber polishing with JB bore paste to slick it out a little bit.
This did work,after about 100 rounds things got to be 100% reliable. So the end effect with a tight chamber is that this rifle is a tack driver,
like no other 308 I have seen. Now if you continue to have problems call DPMS..
Woops did not read last post as you have gotten it going !!!
Enjoy
John

The AR 10 is not new,In fact the first AR's Geene Stoner invented were in 308,he was told by the Army to scale down the rifle
to accomadate the smaller 223 remington ...
5 more model's later came the AR 15 (223 rem or 556 cal)
This platform was designed for 308 and they are awsome.I almost bought the original Armalite 10 about  30 years ago,but could not find mags.
It went for 600 bucks at the time used,now probably would be 3 thousand for an original or more !!!
Later
John

My brother has had quite a struggle with the S&W .308 AR and getting it to work reliably. Several trips to gunsmith cleared up the problems.
1. Rough chamber
2. Mis-aligned holes in gas block and barrel.

Gunsmith claimed that was the two biggest reasons for malfunctions in factory ARs. The hole alignment can be an installation problem or differences in tolerances between the barrel port and gas block construction. The smith had so many of these AR's coming in that he bought a bore scope to run down the barrel to visually confirm gas port alignment. You cannot rely upon "it looks installed right".

Hope this sheds some light on issues .308 AR owners are having.

5.56 and .223 Remington didn't exist when the AR15 was designed, and it was engineered around the .222 Remington.  The 5.56 came from the .222 Rem.

I'm having a similar problem with my 2009 LR-308. See my post. Can you explain how you opened up the gas port? Did you use a drill press or hand drill, etc.

After removing the gas block and confirming it was not misaligned, I used a .076 drill bit which is wire guage drill #48.
My gas was initially .070.

I believe the range for CARBINE GAS TUBE is .070-.085 something like that, so I went to the middle and it runs great.
If you have rifle gas or mid gas it may be a little different.