LR308 troubles (SOLVED)

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[ARCHIVED THREAD] - LR308 troubles (SOLVED)

Posted: 9/25/2016 8:46:17 PM EDT

Let me list the parts, then I will get to the problem..

Juggernaut Tactical Billet DMPS pattern upper/lower set
D Wilson BCG
Faxon 16” Midlength .308 barrel
Seekins Precision Adjustable Gas Block
JP Silent Capture Spring (AR10 Standard)
DPMS Buffer Tube (AR15 Carbine)
Magpul Gen3 LR/SR 10rd magazine
PWS Muzzle Brake
DPMS Lower Parts kit
Magpul ACS-L Carbine Buttstock
Houge Grip
Midwest Industries 15” Handguard

Now for the problem. I am having a bunch of double feed, failure to eject and stovepipe problems. I have tried adjusting the gas block from all the way closed to all the way open. When it does eject, it is either to the 1’oclock and it flys, or to the 3’oclock and it literally pretty much just falls to the ground.. almost straight down at my feet. It does lock the bolt back to the rear on the last round, and once or twice with a few rounds left in the mag. Sometimes it will lock the bolt back, and leave the empty case right on top of the mag.

I am really pretty much stumped as to what the problem might be. I am leaning towards a bolt issue, or a mag issue. But heck, it could be crappy ammo too (PMC Bronze 147gr BTHP.) My next troubleshooting step is going to be trying a metal DPMS style mag. Then I am going to try some different ammo. If there is any insight that could be provided, I would appreciate it. If I missed anything that you need to know, just let me know and I can get you what I can. Thanks so much.

Posted: 9/26/2016 12:22:12 AM EDT

[#1]

I'd say your ammo and mags are ok so I wouldn't worry about those. No gas, no eject.
I'd look at the extractor, maybe it needs more tension.

Posted: 9/26/2016 11:01:36 PM EDT

[#2]

Pull the way back on the charging handle, and tell me where the face of the bolt stops against the back of the ejection port edge.

Ideally, you want the bolt face to stop 1/4" to 1/8" in front of the back edge of the ejection port window.

If the bolt is retracting back past the back edge of the ejection port window, then for now, pull the buffer and recoil spring and start dropping quarters down the tube to use as end of tube spacers to get the bolt to stop the correct distance in front of the back of ejection ports window edge.

As for the bolt, cam a spent case off the extractor, to cam the ejector into the bolt face channel a few times. The extractor should be under a lot of spring tension, but should not be biding up as its moving in and out of the bolt face channel for it.

Hence the fact that you can get the bolt to lock back on the catch (face of the bolt and not just under the carrier), tells me that you have room to correctly adjust the gas block, but either the spent case is tagging the ejection port window edge on the way out, or the ejector is binding in the bolt face channel isntead.

Posted: 9/26/2016 11:15:34 PM EDT

[#3]

Quote History

Quoted:
Pull the way back on the charging handle, and tell me where the face of the bolt stops against the back of the ejection port edge.

Ideally, you want the bolt face to stop 1/4" to 1/8" in front of the back edge of the ejection port window.

If the bolt is retracting back past the back edge of the ejection port window, then for now, pull the buffer and recoil spring and start dropping quarters down the tube to use as end of tube spacers to get the bolt to stop the correct distance in front of the back of ejection ports window edge.

As for the bolt, cam a spent case off the extractor, to cam the ejector into the bolt face channel a few times. The extractor should be under a lot of spring tension, but should not be biding up as its moving in and out of the bolt face channel for it.

Hence the fact that you can get the bolt to lock back on the catch (face of the bolt and not just under the carrier), tells me that you have room to correctly adjust the gas block, but either the spent case is tagging the ejection port window edge on the way out, or the ejector is binding in the bolt face channel isntead.

View Quote

Thanks... I will check that. I also borrowed a BCG from a friend to see if that could be causing the problem. I will prob be going out tomorrow to see if that fixes it.

Posted: 9/27/2016 11:05:50 AM EDT

[#4]

Well, I took a look at it this morning and this is what I found. When I pull the BCG all the way back, it does travel far behind the ejection port. BUT, when the BCG is resting on the bolt catch, it is nearly flush with the ejection port. A pic showing this..

Now, one thing that I forgot to mention. When I am getting double feeds, it is with a spent case and a live round. Someone local to me said that it is an extraction problem, and that I should get a stiffer spring or an o-ring. Are they the same as the ones using in AR15s? Thanks again for the help.

Posted: 9/27/2016 11:11:10 AM EDT

[#5]

Could be the extractor, they're a common source of issues on DPMS pattern bolts, but it sounds more like your ejector.

Pull the bolt and see how much pressure it takes to depress the ejector.

Posted: 9/27/2016 2:27:03 PM EDT

[#6]

Well, got it figured out. It was the need for an o-ring. Took one off the bolt that belonged to my friend and put it on my extractor spring and it works just fine now. Did two full 10rd mags and a bunch of single shots, and everything worked fine. Tuned in the gas block to give me my 3'oclock ejection pattern and it shoots well. Thanks to those that contributed. I appreciate the help!

Sac

Posted: 9/27/2016 2:32:28 PM EDT

[#7]

This thread might be worth a read.

http://www.ar15.com/forums/t_16_4/42_Hellbenders_guides_to_Ultimate_AR15_and_or_AR10.html

Posted: 9/27/2016 9:54:14 PM EDT

[#8]

Following

Posted: 9/27/2016 10:35:02 PM EDT

[#9]

Quote History

Quoted:
Pull the way back on the charging handle, and tell me where the face of the bolt stops against the back of the ejection port edge.

Ideally, you want the bolt face to stop 1/4" to 1/8" in front of the back edge of the ejection port window.

If the bolt is retracting back past the back edge of the ejection port window, then for now, pull the buffer and recoil spring and start dropping quarters down the tube to use as end of tube spacers to get the bolt to stop the correct distance in front of the back of ejection ports window edge.

As for the bolt, cam a spent case off the extractor, to cam the ejector into the bolt face channel a few times. The extractor should be under a lot of spring tension, but should not be biding up as its moving in and out of the bolt face channel for it.

Hence the fact that you can get the bolt to lock back on the catch (face of the bolt and not just under the carrier), tells me that you have room to correctly adjust the gas block, but either the spent case is tagging the ejection port window edge on the way out, or the ejector is binding in the bolt face channel isntead.

View Quote

Dano to the rescue! He helped me solve the exact same issue with my slab side dpms. He has several recommendations that while would have worked, i just got a new upper receiver and barrel along with a heavy spring and buffer. Its a pleasant shooter now.

[ARCHIVED THREAD] - LR308 troubles (SOLVED)

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