AR 10 DPMS feeding issues

[Jonn264]

Gregg, I have a DPMS AR-10 SASS. I had a similar issue when it was right out of the box. My problem was that it was hard to feed a round into the chamber manually or after firing. The problem was that the buffer didn't go back far enough to get behind the bullet in the magazine. Look on the end of your buffer for a circle dented into it by the screw holding the top of your stock onto the end of your buffer tube. The circle is caused by that screw being too long and every time you fire the gun it strikes the screw. I fixed mine while on the range by putting a washer on the screw. I always said I'd take it out and shorten the screw, but I never did. Don't fix what works. I've included a picture of the buffer with the mark on it.

 

[ARlife4me]

View attachment 361572

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.

 

[C-130 Dude]

View attachment 361359

You said you changed mags. Did you change manufacturer also? From what make to what make? If this is a DPMS mag, check the follower. I had several DPMS mags with the old non-anti tilt followers. Had to change all of them out with new followers. They all had the problem you mentioned. Mag positioning in the mag well can also be an issue. Make sure the mag sits high enough up into the mag well. I have seen quite a few lowers that have the mag stop machined in the wrong location. Usually causes cartridge pick up problems but you may want to look at that. Cycle the gun manually slowly. Look for any change in cartridge feeding angle. You said you polished the feed ramps. This is a problem area with these guns. If those ramps are not right, you will play havoc with trying to get it sussed out. Good luck

 

[Mmac52280]

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

All of mine use the Aero lowers. Not all mags worked without tweaking. I absolutely agree it could indeed be the lower, but slow motion watching it feed a round helps to isolate the cause. He noted the left round feeds, but not the one on the right. If it was both, I would be suspicious of the lower.

 

[Mmac52280]

10's are more temperamental than 15's are on every aspect!

I know a few women who are less temperamental.....I have 3, one in 308, 1 is a 6.5 Creedmoor, and one is a 45 Raptor....all need the mags "massaged" to get them to feed reliably. All the lowers were 100% complete when purchased from Aero.

 

[Beamonk]

If it is not the magazine it is either too much gas or not enough. Check with your gas port size, make sure gas block is aligned correctly. See what size buffer you are running. Magazines can cause alot of issues, too.

 

[wolffo]

my 4 AR10 builds all required "break-in" versus zero break-in for any of my AR-15 builds
including my factory armalite AR10s did not run right out of the box

gas - make sure TDC - double check it

buffer spring - lock the buffer back - let sit - couple weeks (break-in procedure)

mags - sometimes need to be loaded full and let them sit for a few weeks (break-in procedure)

agree on running sloppy wet/lube for break-in on a new build (big bore and AR-15)

BCG - avoid nickel coated - I have $300 in paper weights at this point
I like the nitride coated

 

[wolffo]

are you shooting low power NATO loads ?

 

[wolffo]

I recently diagnosed an issue with magpul sr25 mags for a new Aero build

my two 10 rounders would not lock back on empty

my four 20 rounders would correctly lock back on empty

close examination revealed different followers

the 10 rounders would not clear the right side feed lip enough to allow for lock back
I attempted to sand them to work correctly
no luck yet

an email to magpul revealed that individual SR-25 followers are not available for sale
but I was welcome to buy more mags

 

[cantfixstupid]

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.

 

[wolffo]

agreed on the weight !
mine are so heavy they cannot be anything but bench rest guns
14 lbs with a scope and mount
I use a padded machine gun sling

 

[Mmac52280]

I should have just got the 1 Aero Precision Lower and swapped the uppers when I wanted to shot different caliber.

That's what I tried to do. Every time I opened the safe, the unmounted uppers would start crying...I eventually folded

 

[cantfixstupid]

agreed on the weight !
mine are so heavy they cannot be anything but bench rest guns
14 lbs with a scope and mount
I use a padded machine gun sling

I make my woman carry mine, she thinks she makes a great gun bearer, and so do I

 

[Gregg C]

You said you changed mags. Did you change manufacturer also? From what make to what make? If this is a DPMS mag, check the follower. I had several DPMS mags with the old non-anti tilt followers. Had to change all of them out with new followers. They all had the problem you mentioned. Mag positioning in the mag well can also be an issue. Make sure the mag sits high enough up into the mag well. I have seen quite a few lowers that have the mag stop machined in the wrong location. Usually causes cartridge pick up problems but you may want to look at that. Cycle the gun manually slowly. Look for any change in cartridge feeding angle. You said you polished the feed ramps. This is a problem area with these guns. If those ramps are not right, you will play havoc with trying to get it sussed out. Good luck

Thanks, Dude
It had a Magpul in it, it did the same thing. Got a C-Products, still did it. I believe we're on the right track, cause my mag with shells in it don't look any thing like any of the pics posted here. It's heartening to know and experience strangers offering advice. I really appreciate the time everyone has taken to offer up advice, experience, humor. I'll see what happens Sat or Sun when I go shooting.