An AR-10 Cycling Question

[Fishinfool]

A while back, I picked up a new DPMS 16 inch AR-10 in .308, mainly because it was a good price at the time.

This week, I decided to spend some time with it at the range, and am running into a problem. With 3 brands of M80 surplus ball ammo, it short cycles. When it does so, it will 50/50 pick up a fresh round from the magazine, but not fully eject the empty. With 180 grain hunting ammo it cycles, but only ejects brass out maybe a foot from the gun. I believe it is under gassed. There is no blockage in the gas system, and the gas block / tube appears to be lined up with the barrels gas port. My Armalite AR-10T functions fine with the above noted ball ammo.

Would I be better off putting a lighter buffer / spring in it, or drilling the gas port slightly larger? This is the first AR I have owned with gassing issues, and prefer the least invasive fix, if possible.

Thanks

Larry

 

[lihpster]

Sorry to hear your gun isn't working right. Have you tried calling DPMS? I don't know how long you've had it but they SHOULD be wanting to fix that issue. If not they might be willing to tell you how to fix it. I think your diagnosis is right but I'm not sure how to fix it myself.

 

[Fishinfool]

I would, but shortly after I bought it, DPMS went belly up... Still, for $725 NIB it was a good deal at the time..

Larry

 

[lihpster]

Didn't know they were gone. $725 is a great price. Here in town we have a gun store that specializes in MSRs. If I was stumped I'd probably go there to get answers. You got something similar near you?

 

[serger]

I assume you've cleaned it really good and then lubed it really good.

If you've done that then I would get an Odin Works adjustable buffer
and play with the weights. That's the cheapest way to start.

Odin Works Adjustable Buffer - AR-10

 

[Eric300]

My buddy has the same rifle and encountered the same problem He sent it back to DPMS and 9 weeks later got it back with the same fail to extract/eject issues. He brought it to me and after giving it a once over and a few test shots, it was in fact 'short stroking'. The gas block on his rifle is secured to the barrel by set screws (which I hate. Pinned gas blocks are the way to go, especially on a 'Fighting Rifle'). I don't recall whether it had one or two set screws. Anyway, I removed the gas block, checked everything over and determined that the gas block was slightly misaligned with the gas port on the barrel. It doesn't take much misalignment to cause problems. That's a known issue with screwed on FSGB/GB. So, I properly aligned the gas block, dimpled the barrel where the set screw contacted and tightened it/them down about as hard as I could. Inserted a 10 round mag and dumped it as fast as I could pull the trigger with zero malfunctions. Problem solved. Before you start dumping time and wasting $$$ on stuff you don't need, CHECK THE GAS BLOCK ALIGNMENT FIRST.