AR feed problems...

rushthezeppelin

TGT Addict
Dec 28, 2012
3,821
48
Cedar Park
Was out at BOTW today with Breakingcontact and after my first mag which went clean I started having feeding issues. No ejection issues at all, rounds seemed to spit out the normal 10'-15' but either it wasn't stripping a round off the mag at all or it would jam them bullet up into the locking lug area of my barrel marring up the rounds pretty badly. It started out every five rounds or so but once I got to about 5 or 6 mags in it was doing one or the other problem on every shot. Tried eliminating mag problems, tried 4 different Pmags 2 gens 3s and 2 gen 2s and even a GI that BC let me borrow. Went and traded some 556 with one of the guys in the other bays and same problem. I had just switched from an A2 birdcage to a Miculek brake and tried switching back to the birdcage, same problems. Talked to Eric in the shop and he suggested it was either a problem with the gas system (which he wasn't sure of as he says usually you get ejection issues with that as well) or a dirty buffer tube.

Got home and inspected the buffer tube which I've never cleaned but it seemed to have almost no carbon at all just a light film of cold, gunky (but clean) frog lube which should have warmed and slicked up I would think. Then I ran a pipe cleaner with some frog lube through the gas key which didn't seem insanely dirty certainly not blocked up and it dawned on me that I haven't put the obligatory drop of lube in the gas key in at least 500 rounds (gun is around 1200-1300 round count and only ever had problems with a bit of steel I put through it around 1k). Could that lack of lube in my gas key have caused the cycling issues? If not any other ideas as to what could be causing this? As Breakingcontact can attest to, everything else on my bolt was properly lubed up. Could it have been the cold sludgy frog lube in the buffer tube? Would it even warm up enough in there to get it slick, which could explain why it was fine for the first mag while it was still warm from the car but after leaving it on the bench and shooting a few mags out of my pistol and coming back it was cold and sludgy and never warmed up?

Need some ideas here, want to get my trusty DPMS back into the HD rotation instead of relying solely on my 9mm.
 
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Shorts

TGT Addict
TGT Supporter
Mar 28, 2008
4,594
38
Texas
Short stroking? Can you get specific on the ammo used? Buffer weight & spring?

Any way to try a different lower on that upper to rule out any dimensional issues in the magwell?

If you didn't get a chance to run it well lubed, would be worth knowing though.

On the gas key, BCG and tube, does the BCG slide smoothly when it closes up and opens? I have read of slightly off center gas tubes that cause just enough friction o the gas key to bind it up.
 

9x19

Active Member
Aug 11, 2008
689
36
Doesn't a short-stroke usually result in an ejection issue?

Since extraction and ejection were normal, and if the BCG was lubed properly, then it almost has to be the gunky lube in the buffer tube, slowing the return stroke. That buffer tube spring's main job is returning the bolt to battery.

Good luck.
 

rushthezeppelin

TGT Addict
Dec 28, 2012
3,821
48
Cedar Park
Short stroking? Can you get specific on the ammo used? Buffer weight & spring?

Any way to try a different lower on that upper to rule out any dimensional issues in the magwell?

If you didn't get a chance to run it well lubed, would be worth knowing though.

On the gas key, BCG and tube, does the BCG slide smoothly when it closes up and opens? I have read of slightly off center gas tubes that cause just enough friction o the gas key to bind it up.
Ammo was AE 223 for almost all of it and about 5 Independence 556 that I traded for at the end of my day. Buffer weight and spring are I assume standard milspec, w/e comes with the DPMS Oracle.

As to a different lower, BC was a dummy and decided not to bring his AR :P otherwise I would have had a control to test against on that. As far as I know the mags sit just the same as they always have in my lower and would feed perfectly fine when inserting a new mag and hitting my bolt release.

Didn't get a chance to run it with lube in the gas key as my dumbass left my froglube at home. BC offered some of his Mpro7 but I've heard of bad things happening when mixing FL with any other petroleum based lubes.

As to the tube alignment everything seems to be fine although I did switch gas blocks not too long ago to put a FF tube on. It doesn't seem to be off and ran fine for at least 200 rounds after the change and before today. Granted it is a little hard to tell since if its off since I'm feeling the bolt turn in the carrier (took upper off lower and am pulling in and out on the back of the carrier). Might loosen the gas block and to try and see if I can get it to feel any different.
 
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rushthezeppelin

TGT Addict
Dec 28, 2012
3,821
48
Cedar Park
I think I'm going to probably end up degreasing my buffer tube and just using a slick when cold lube then. Ohhh shoot I almost forgot to mention I've been having problems with bolt lockback for quite a while. At first it was just with my thermold 20s and then it started happening more and more with my pmags. I think that pretty much settles it with that evidence, don't know why I didn't make that connection till now.

Also anyone have a suggestion on a general purpose degreaser to use without having to grab a fancy gun degreaser from a gun store? Something like simple green perhaps?
 
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breakingcontact

TGT Addict
Oct 16, 2012
18,298
38
Indianapolis
Id blame it on your range partner! I didnt think of popping the buffer tube out. I usually keep them dry or with just a wipe down of the spring with a lightly oiled cloth. If the lube back there attracted enough junk it may not be compressing all the way or too slowly?
 

40Arpent

TGT Addict
TGT Supporter
Jul 16, 2008
7,055
48
Houston
Also anyone have a suggestion on a general purpose degreaser to use without having to grab a fancy gun degreaser from a gun store? Something like simple green perhaps?
Non-chlorinated brake cleaner. Just keep it away from the plastic.

If you do use Simple Green, make sure you rinse well with water. Simple Green likes to eat aluminum.
 

rushthezeppelin

TGT Addict
Dec 28, 2012
3,821
48
Cedar Park
Id blame it on your range partner! I didnt think of popping the buffer tube out. I usually keep them dry or with just a wipe down of the spring with a lightly oiled cloth. If the lube back there attracted enough junk it may not be compressing all the way or too slowly?
The lube itself was pretty darn clean just that damned tendency of froglube to congeal when cold is what got me I think. Soon as it got to that 40* ambient temp it started negatively impacting the speed of the buffer. Will report back once I clean it and get to the range again so all you other people who use frog lube know to watch this.

Non-chlorinated brake cleaner. Just keep it away from the plastic.

If you do use Simple Green, make sure you rinse well with water. Simple Green likes to eat aluminum.
Awesome, thanks. Pretty sure I have some brake cleaner in the garage. I'll make sure to take my stock off and be careful not to get any on my ergo grip. As to mopping it up should I just stuff the tube with a paper tower or something
 
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