DPMS LR-308AP4 failure to extract

[ArturoJ]

I friend of mine has a DPMS LR-308AP4 that fails to extract lots/most of the time. He has used LC, Australian, SA, Portuguese surplus and others that I forget now. The fired case sticks in the chamber. Sometimes a piece of the case head is ripped off (SA), sometimes the extractor slips off the case. Sometimes he can close the bolt on the spent case and manually eject the case, sometimes he needs to use a rod to tap the case out of the chamber.

DPMS says to use good ammo. He has had the same problem with Winchester white box, just less often.

It seems to me like a chamber problem to me, but what do I know. Anyone else have/had this problem and found fix?

[bigbrowndog]

take a set of go-no-go gauges and check the chamber, you can also polish the chamber, clean the chamber, mistakes can happen when machining. if its a chrome moly barrel with a chrome lined chamber/bore I would not suggest polishing the chamber.

trapr

[TRUBL]

How old is this rifle??

When the shells do eject.....are they dribbling out? or do they fly out!!

Tim

Edited June 18, 2008 by TRUBL

[GentlemanJim]

Is it a 16" barrel?

It kinda sounds like the bolt is unlocking while pressure is still too high in the barrel

But just like Trapr said ...a rough chamber or incorrect chamber could also do it

Please Let us know what you find

Jim

[ArturoJ]

Trapr:

Chrome moly barrel, not chrome lined. I am not sure if he has the gauges, but GG&G should be able to check it out.

Tim:

He has had it for about 3 months, could be old stock from the dealer. I have not watched the ejection myself, I will ask.

Jim:

Yes, 16 inch. It Could be high pressure at unlock time but I am in the "rough chamber or incorrect chamber" camp. High pressure/early unlock and chamber problems at the same time would make this problem even worse.

The owner is an experienced long time shooter that is perplexed by this problem. He had a LR-308B that worked great with everything stuffed in the mag, he should have kept that one.

Art

[smokshwn]

I am thinking there could be a chance that the gun could be over gassed. 308's in the ar platform usually have plenty of gas as it is, I would think the 16" makes for an even narrower operational range.

[psyops]

Art,

I have the exact same DPMS system as you, I think. I had this happen to me yesterday. I was using Russian Brown Bear crap, and I token alot of my FTE problems with that. I pushed 100 rds. of Federal American Eagle without a problem. So we'll see.

If I have it with other ammo I'll keep you informed. Have fun and good luck.

-Mike Patrick

[psyops]

Art,

Sorry, as your friends gun.

-Mike

[M ammo]

I have the LR .308 18 inch heavy barrel, and I have the similar problem.

I know two other people that have the same problem.

Most of the time if it fails to fire, I have to use a screwdriver to pry the bolt carrier back. To get the round out.

I have used all types of ammo.

I intend to shoot my re-loads for the most part. And I might say, they are much better than you can buy at the store.

I have not had the time to put in to this rifle to get it up to par.

I have heard I might need to send it back to DPMS, to get it reamed out a bit.

[bigbrowndog]

JP's video on gas rifle basics is a very good thing to watch and garner info from, even if you are an old hand at shooting. I remembered things i'd forgotten and learned some new ones. John's info on checking ammo is very important when it comes to reliability. you might drop check the ammo as well.

For polishing I've taken a once fired case from that rifle and coated it with rouge or flitz and attached it to a rod section and spun it on a drill, you can also do it with a fat chamber mop.

Trapr

[M ammo]

JP's video on gas rifle basics is a very good thing to watch and garner info from, even if you are an old hand at shooting. I remembered things i'd forgotten and learned some new ones. John's info on checking ammo is very important when it comes to reliability. you might drop check the ammo as well.

For polishing I've taken a once fired case from that rifle and coated it with rouge or flitz and attached it to a rod section and spun it on a drill, you can also do it with a fat chamber mop.

Trapr

I'll have to give that a try,,

I chamber gage every round.

I'll have to look up JP's video,,, probably on the web site.

[nm3gnr]

look really close at the extractor. I have a friend with one of these and he carries 5 extractors with him. He goes through about that many every yer in about 2000 rounds.

[mvpete]

had the same problem, tried all the things you have suggested

called dpms, warranty dept, they said send it in

i dropped it off at 1:00 pm they asked if i could wait while they test fired

he came back in 10 minutes asked if i could come back in 1 hour

dpms replaced the rough barrel, extractor looked ok

NO CHARGE

also added a adj gas block

rifle has run 100% since

[aka JW]

had the same problem, tried all the things you have suggested

called dpms, warranty dept, they said send it in

i dropped it off at 1:00 pm they asked if i could wait while they test fired

he came back in 10 minutes asked if i could come back in 1 hour

dpms replaced the rough barrel, extractor looked ok

NO CHARGE

also added a adj gas block

rifle has run 100% since

Thats good customer service. I have a 16" model and haven't had any problems so far. Jim

[ArturoJ]

My friend’s rifle has been sent back to DPMS. The last time at the range he had failures to extract every time with Remington, Winchester and Federal ammo. We will see what DPMS says.

Thanks to all for your help.

[swandme]

Just picked up a couple of the LR 308's in 24 SS bull

The first 308 is a tack driver. today w/ the Custom comp 168's and 42.2 2520 3 shot @ 100 = .33 in

but with the Rolling thunder brake installed.

Thats the good news

Bad news is function is less than 70 %

The I am getting FTF bolt sticks open 1/8 in and To get it out I have to smack the but stock down on the bench and the weight of the Bolt extracts it .

I checked all the rounds that were stuck and most of them passed the dillon case gauge. there was a couple that stuck out the bottom .0005 from the high platform.

The Fired cases are rough as well .

I did manage a few rapid fire stings but overall not good.

The chamber is rough as a cob . What is your advice on chamber polishing ?

The Second one the chamber is so rough I only fired 3 rounds 2 of them had the rim pulled off

so I had to knock them out with a cleaning rod.

Should I try to polish it or send it to DPMS

I am afraid to ask them quessing the will want them back and screw up the Accuracy on the good one .

What Say you ..... ?

Re: DPMS LR308 failure to extract [Re: kilo7788]

ajwarrior

Private First Class

Registered: 03/26/10

Posts: 3

Loc: Atlanta, Georgia

JonF has given me solid info and advice on my lr308. Like kilo said they do require lots of oil in the beginning and yes some polishing may be necessary. Just make sure your lr is cleaned well and super wet. And more creds to kilo for advising on the DPMS forums, have been on their forums for a months now.

Edited by ajwarrior (03/29/10 12:33 PM)

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#1721103 - 03/28/10 05:36 PM Re: DPMS LR308 failure to extract [Re: ajwarrior]

chpprguy

"weld imitator"

Registered: 02/08/04

Posts: 1895

Loc: Los Alamos NM

the model is a LR-308 caliber 308 (stamped on the lower)

I see no markings on the barrel, i'll remove the sight and handguard and look for markings.....

this model....

I am not the original owner, so I am unsure of the break in or care of the rifle, prior to my owning it.

I will clean it again thoroughly and look at getting an adjustable gas block... and inspect the chamber as best I can,

I need to get the appropriate tools to remove the barrel...

I may just turn it into a 7mm-08, I'd just like to get it functioning correctly first...

Edited by chpprguy (03/28/10 05:37 PM)

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#1721243 - 03/28/10 06:34 PM Re: DPMS LR308 failure to extract [Re: chpprguy]

Unknown

Sergeant

Registered: 09/17/09

Posts: 62

Loc: Oregon, USA

I had similar problems with my DPMS LR308. Stuck cases, bullets jammed into the throat...I eventually decided that it had a short throat that caused excessive pressure and the function problems.

I returned the rifle to DPMS for repair. They said they had feeding problems and replaced the magazine. I had never had, nor did I ever report any feeding issues.

Funny thing is that the rifle now works like it should. I suspect that they fixed the short throat, and simply couldn't bring themselves to admit to a quality control issue. Rather than admit that their throating reamer wore out prematurely, they appear to have fixed my rifle and lied about it. I no longer have the rifling engraved on bullets of rounds that have been chambered but not fired.

Whereas I'm happy that the rifle runs normally now, I am very disappointed in being treated like I'm too stupid to recognize that they fixed the precise issue I complained about. It makes me not trust them anymore.

You might want to check for a short throat...my rifle also ripped the rim off cases that were stuck in the chamber before the rifle was returned...it hasn't happened since I got the rifle back...what would you think?

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#1721303 - 03/28/10 06:57 PM Re: DPMS LR308 failure to extract [Re: chpprguy]

CDAT

Lance Corporal

Registered: 12/30/06

Posts: 37

Loc: Texas

chpprgy, FYI and consideration, I had the same issue, extractor ripping case rims off, with my DPMS LR 308. However, it would only do it with reloads, never with new US made or US MilSup ammo. I installed an adj gas block and started using a small base resizing die on the cases I reload and shoot in the LR 308, After that the problem went away with one exception. When using Federal small based sized cases it would still sometimes rip a rim off. I have been told that Federal brass is soft (could be an issue with your brass/ammo also)and I may not be getting a true SB sized case when I process it. The alleged brass softness may have been affecting the rate and amount of case spring back, causing the case remain sealed to the chamber longer after firing. Now I only use small based sized LC and Win Brass when reloading for this rifle. I was also told, when I purchased the rifle, that DPMS 308 chambers are on the small end of the tolerance scale.

: DPMS LR308 failure to extract [Re: sinister]

gunfrog

Private First Class

Registered: 01/10/10

Posts: 3

Loc: Northern Virginia

I had the same problems with my DPMS 16" 308 AP4, tried all the fixes: polish chamber, adj gas block, heavy buffer, AR carbine buffer tube and spring, moved gas port to mid length, and various combinations. Had some improvement but still had issues. I built another one with 762 chamber and it runs great.

Got me thinking so I finally checked the chamber in the problem gun and it closed on the no-go gauge. So I sent it off to very knowledgeable gun smith, to get the actual chamber dimensions and have it reset to 762. Still waiting on its return. Will advise.

Suggest you check your chamber with a set of gauges.

All the early DPMS guns of this type where made in 308, now DPMS only offers it in 762. They used to offer a 762 reamer to improve reliability with surplus ammo. They no longer offer the reamer, nor will they redo a 308 chamber to 762, based on a phon con I had with them about a year ago.

Edited April 8, 2010 by swandme

[sleepercaprice1]

JP's video on gas rifle basics is a very good thing to watch and garner info from, even if you are an old hand at shooting. I remembered things i'd forgotten and learned some new ones. John's info on checking ammo is very important when it comes to reliability. you might drop check the ammo as well.

For polishing I've taken a once fired case from that rifle and coated it with rouge or flitz and attached it to a rod section and spun it on a drill, you can also do it with a fat chamber mop.

Trapr

I'll have to give that a try,,

I chamber gage every round.

I'll have to look up JP's video,,, probably on the web site.

I have a LR308T and had similar extraction problems with it when it was new. I polished the chamber as described above using a fired case, I added an "O" ring to the extractor spring, added a tungsten weight from a H1 buffer and installed an Armalite AR10 buffer spring, which is a little longer then the DPMS spring, which may mean a bit more strength. My thinking is that the added weight to the buffer and stiffer buffer spring delays bolt opening. My rifle now runs nearly 100% with US ammo or my own loads. It's still somewhat problematic with some foreign surplus. My belief is that the chamber is tight in the neck area and cases with thick necks may cause extraction problems.

[OUshooter]

So I'm chasing the same issue with my LR-308. The weird part is that I've run 2k rounds through this thing with a mixed bag of handloads and factory, with no issues. Then one day it just took a dirt nap. I've tried different ammo, the o-ring trick, and adjusting the gas block. I finally got the cases to come out of the chamber but they just sit on top of the empty mag with the bolt locked back. I haven't yet found a set of go/no-go gauges. But it's been running great for over a year till this week.

Could I just have a wore out extractor?

Thanks,

[djeffers]

When I got a 16" AP4 barrel I wound up taking to a local gunsmith who had to ream the chamber and changed the extractor springs, after that it has ran fine. But, when I first got it, it wouldn't even go all the way into battery.

I wish I would have thought about sending to DPMS, it might have saved me $120. But, I was in a hurry and wanted it ASAP.

[barrysuperhawk]

When I got a 16" AP4 barrel I wound up taking to a local gunsmith who had to ream the chamber and changed the extractor springs, after that it has ran fine. But, when I first got it, it wouldn't even go all the way into battery.

I wish I would have thought about sending to DPMS, it might have saved me $120. But, I was in a hurry and wanted it ASAP.

Another data point, I had a AP4 that would do the same thing when I tried to run it dry [little or no lube]. I tried everything, I spun a chamber brush in a drill, I futzed with the gas, swapped ammo, the whole mess, but what worked is running my gun dripping wet with the lube no heaver than motor oil [no grease]. I now have 2 DPMS and a Bushmaster and they all run flawlesly when I keep them wet [as in a shot of remoil or CLP before every stage, on the bolt and carrier.] I am not saying that the other solutions are wrong, but that is what worked for me in my guns.

[casanovaracing]

Hooray, I can say something that might be helpful... DPMS 308s are great, I've had several and I've had this same problem on a couple. EVERY time I have had this it was solved by replacing the gas block. The factory block is very open and the over-pressure causes exactly what Jim said. The give away is the removed case rims (or very stretched on the ones that do extract). That said, polishing the chamber is always a good idea on any rack grade 308 barrel. And all ARs should be run WET! (I know some of the piston guns say otherwise but...)

[pyrrhic3gun]

A friend and I both had similar extraction issues with DPMS LR-308's.

Both were fixed by using the "dual extractor spring" that used to be available from MidwayUSA.

Currently Midway has a note that says they have been discontinued (P/N 349127).

Here is a link to DPMS's store with a similar part (P/N 308-BT-08)...I don't know if this is the same as the one I used (mine had a K suffix on the P/N). You might want to confirm that before ordering. Don't expect to receive an inner and outer spring...I just got a spring that was about twice as long (that's the dual part I guess) and stiffer. I added two of the #1 o-rings that I usually use on AR15s and haven't had any more extraction problems.

[pyrrhic3gun]

Like I said here is a link blah, blah :^)

http://www.dpmsinc.com/Bolts--Pins--Offset-Parts-_c_117.html

[DEP44]

My AP4 came with the inner and outer extractor spring. Same thing, the empty was extracted but not ejected. Laying on top of the mag .

A Wolff extra power extractor spring didn't do nothing. The double O ring trick was the cure.