DPMS AR-15 Carbine Malfunction

[ahays07]

I've been having some issues with my DPMS 5.56 AR-15 carbine. I currently use a 50 gr .223 Fiocchi round with a red plastic bullet tip. I have two 30 round magazines that came with the rifle. I normally only put 20 rounds in each magazine to help conserve on ammo (or else I could easily burn through the entire box in one outing).

The first mag goes through fine with no malfunctions and a consistent ejection pattern. The second mag I can get approximately 5-8 rounds off before the malfunctions start. The round will fire, extract, and eject but it won't put a fresh round into the chamber. This occurs every round after the malfunction starts.

I've read that DPMS rifles need to be very well lubricated. I've already tried heavily lubricating the bolt before I go to the range and after the malfunction occurs. The lubrication after the malfunction occurs helps slightly and allows for approximately 5 rounds before the next malfunction. The ejection pattern is still normal when the malfunction occurs.

I have already replaced the bolt gas rings under Scheels recommendation. I've talked to several people about this issue and the common idea is there is not enough blow back and that the gas tube will have to be replaced. Before I drop money into a new gas tube replacement I wanted to see if anyone else has an idea.

 

[Nicky Santoro]

What brand magazines are you using?

 

[ahays07]

Just the factory DPMS 30 round magazines that came with the rifle.

http://www.dpmsinc.com/DPMS-223556-30-Round-Magazine-Black_p_674.html

 

[HB]

How much lube are you using? It may be getting burned up and baked on if your gun is really that wet.

HB

 

[ahays07]

When the problem first started I was just using a thin layer of lubricant and spreading it on the bolt with my finger. The last time I cleaned it I pinched the bolt between my fingers and sprayed it down with the lube can after I was told by Scheels it needed to be dripping wet. This fixed the problem temporarily and I was able to put 40 rounds down range without any trouble. The next time I had it out it was acting up again. One of the guys recommended a lubricant that works very well at the shooting range. I used the recommended 2 drops in both of the holes on the side of the bolt. This fixed the problem once and the last time I was out it acted up a few more times after but for the most part it helped.

 

[BBBBill]

ARs like to be run wet. Don't let anyone tell you different. My experience with them since the 70s beginning with my first CAR-15 through 33+ years in the military showed that to be true. That said, other things may be at work here. A miniscule gas leak may be enough to cause failure to feed with a little fouling of the action with carbon from firing a few rounds. Check your gas key to ensure that it's bolts are tight and well staked. Start with that before looking elsewhere.

 

[ahays07]

I'll double check that when I get a chance. The last time I had it apart it looked fine but I didn't thoroughly inspect it either.

 

[joem1945]

Put a little white out around the gas block to see if it leaks when hot.

 

[The Bushmaster]

One or both magazines. Or have you tried to determine if it might just be one of the magazines?

 

[ahays07]

Sorry for the late reply I've been busy with work. I have actually tried both mags to see if they were causing the malfunction. When the malfunction starts I tried loading 10 rounds into both mags. Both mags were still malfunctioning.

How easy is it to get the whiteout off the gun once its on there?

 

[boom boom]

Acetone, aka nail polish remover, gets the whiteout off. Tip, use a Q-tip and the minimal amount of whiteout necessary.

 

[USAF_Vet]

Have you lubed your buffer spring?

My DPMS would run bone dry until I switched to a mid length gas system. Dripping wet is a little much, but a good film on the bolt and buffer spring should be enough. Don't use anything thicker than something like RemOil. Too high a viscosity can slow down the bolt.

If you can, go buy a Magpul (or other quality brand) magazine, just to make sure it's not the mystery mags from DPMS. If the springs in the mags aren't to spec, it might not be pushing the next round up fast enough to be stripped out and chambered.

But, if the bolt isn't coming back far enough, it'll extract, eject, reset the trigger and cock the hammer, but not be back far enough to strip the next round. A lot of things can cause that malf. Lube too thick, not enough lube, binding buffer spring...

If you've recently changed anything go back to what you were doing before it started having problems. If nothing has changed, try a different mag.

I just had a similar issue with my frankengun.

 

[Highcaliber]

Have you tried different ammo? That 50 gr pill and being .223 pressures may not be enough to cycle properly.

Try a mag or two of Federal XM193 5.56 Nato, before you start troubleshooting too far.

 

[dcloco]

Is the gas tube aligned properly and clean?

Have you lube the buffer & buffer spring?