AR 10 DPMS feeding issues

[Gregg C]

are you shooting low power NATO loads ?

Yup. Nice and cheap for break in. Believe pressure is all over the map. Will be mounting up the Mag Speed this weekend as well, to find out how much they vary.

 

[Gregg C]

Rifle length buffer, but I still don't know if he's using that or carbine. Not even for sure what length buffer tube is used also. Armalite with dpms parts or vice versa is a no go! Well except for some parts. AND yes there are receivers that will fit armalite and dpms, example matrix arms for 1.

In my ignorance, I titled as AR-10. It is not in fact an AR-10. Sorry for the confusion. It came from DPMS, and now that I think about it, it is an LR-308. Hope I got that right.

 

[Gregg C]

Not to be this guy but you might want to delete first paragraph of your comment. Building your own gun is legal without serial number. However buying an 80% someone else made gets you both in trouble. Unless its serialized, but ur comment did not say so...

Just went back and re-read my post. It should say built by a friend of mine and I . He basically held my hand thru it. Thank you for looking out for me.

 

[ARlife4me]

In my ignorance, I titled as AR-10. It is not in fact an AR-10. Sorry for the confusion. It came from DPMS, and now that I think about it, it is an LR-308. Hope I got that right.

I call every large ar platform ar10, so no worries. Most I've seen are lr/sr25 (dpms style) compared to ar10 (armalite) and their bcg, buffer assemblies and gas systems are a hair different. Rock River uses armalite buffer and gas systems, but uses fal mags (may have changed). I have receivers that are armalite cut, but dpms compatible. Barrel nut threads are a different pitch between the 2.

 

[wolffo]

on the Nato loads for break-in…..
good idea…and cheap
but have you tried any full power 308 loads ?

 

[Gregg C]

on the Nato loads for break-in…..
good idea…and cheap
but have you tried any full power 308 loads ?

Well, no hand loads, yet, but I have put a couple boxes of W-W, and some Remington CoreLokt. Neither of those are considered premium, but maybe a touch better stuff. Did the same thing.

 

[wolffo]

got it, so you can rule that out
hunting ammo is hotter than Nato
and therefore cycle harder

are you using a clamp-on or set screw gas block?

 

[UncleDano]

On one I built and was having similar issues. tried everything gas & spring related. I did a slow mo recording into the ejection port with just one round loaded. It was dropping the casing on the way out. put a stronger ejector spring & o-ring on the ejector and problem fixed.
Just my two cents worth.

Do you mean extractor or ejector?

 

[UncleDano]

Gregg:
I was in the first thread trying to help you. You are getting advice that is all over the board here. I'm sure the intentions are good.
The information item I see missing from the other thread is your statement the bolt carrier group sometimes does not come all the way back and misses the base of the second cartridge which hits the center of the case causing a jam and dent.
Is this still the situation?
If it is, the bolt will not strip the round from the mag and chamber it.
I do agree with the detailed information Cohunt provided. The cartridges should have a slight nose up position in the magazine. This is easy to accomplish and then we can move on to other diagnostics.

very important point, if bcg does not come all the way back!! Is this mentioned in OP?

 

[UncleDano]

There is an inherent issue with a lot of the 80% LR308 type lowers. I believe it has to do with how the mags are held in the lower. I think they are held too low. I saw the exact thing on a friends build. It would double feed constantly. He tried an adjustable gas block, buffer and spring.
Even tried 3 different types of mags.
Nothing worked.
He finally changed the power to an Aero Precision 308 lower.
The gun runs flawlessly.
It was the lower

When you say double feed, is it double firing? What exactly does a double feed look like?

 

[VNPathfinder]

A lot of good suggestions here and possible solutions. If you want to try the barrel shims , they can be had at Ar15handguard.com, product MTR308SH for $10. Good luck.

 

[cohunt]

A lot of good suggestions here and possible solutions. If you want to try the barrel shims , they can be had at Ar15handguard.com, product MTR308SH for $10. Good luck.

I've always used the shims to correctly space the barrel/nut for proper gas tube alignment -- never thought of them for "extending" feed ramp depth.

 

[grandedirt]

I have 3 AR10's they are a finicky beast at best, the 6.5 Needmore functions flawlessly, its Aero Precision top and bottom and is a tack driver will eat any kind of ammo you put in it, heavy as hell but shoots great. # 2 - DPMS Upper 308 and PSA Lower, sometimes it works sometimes it doesn't had to do some grinding on the lower to get the BCG to lock back and it likes a 5.5 ounce buffer, not a 5.4 or 5.6 or any other flavor, just 5.5 I have several of the others as conversation pieces. It will only shoot premium match ammo and nothing less than 150 grain pills and those are iffy after 100 or so rounds, PMags are the only magazines that will work. #3 Lewis Machine & Tool Lower - Wilson Combat Upper in 243 Win, the stripped lower cost more that the complete upper, this combination was supper tight, did a little honing and polishing at the interfaces that helped, this one had mag issues little tweeking on the front lips fixed that, it has issues with cheap ammo as does the 308 so its handloads only for this one and it did take some time to get it broke in where it is basically consistent. I attribute # 2 and # 3 issues to different Mfgs of the components. Those 80% things are not high quality, I am willing to bet if you get a good lower all your issues will disappear. PSA is not a good lower! <(Read That Again) I have tried putting all the uppers on the PSA, it is a disappointing disaster every time. All of the uppers function good on the Aero Precision and the Lewis Machine and Tool lowers. I should have just got the 1 Aero Precision Lower and swapped the uppers when I wanted to shot different caliber. They all weigh so much that unless you are the Hulk you cant shoot 2 at the same time anyway. Get a good quality lower, save the headache and frustration and have fun, its only money.

If I'm not mistaken, and I may be, the PSA 308 lowers/uppers don't play well with other manufacturers. I thought they were somewhat proprietary.
I think that the issue w 80% 308 lowers gets into the fact that there is no "standard" with the "LR308" type platform.
I'm sure that someone has had a successful build with a 80% 308, but I've read about more failures than successes with it.
I've stayed away for that very reason.
Someone with more knowledge could probably correct my thinking.

 

[Citified]

UncleDano
I believe this was mentioned in the other post before this one was started at the request of the other poster. This is a new post started by Gregg C. Somewhere in that lengthy listing he mentioned the bcg not coming fully rearward when fired but hasn't said anything about it since then.
He has stated if he locks the bcg fully back with the stop and single loads from the mag, it chambers ok.
Cohunt has suggested the cartridges are not sitting properly oriented in the magazine and Gregg seems to agree his are not nose up. He was going to fix this by tweaking the mag lips and test fire it this weekend