AR10 Failure to Cycle

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9 years 4 days ago #46855 by bubbagoes
AR10 Failure to Cycle was created by bubbagoes
I also have been having a failure to feed problem, or I should probably say failure to cycle completely. I'm pretty frustrated with this problem. I decided to build myself a AR10 style rifle, so I built it out of a Aero Precision Lower, and upper, with a 20" LR 308 barrell..From the beginning it has failed to cycle completely, usually throwing the brass out about 2-3 feet at about 2:30-3 o'clock position.. However it would not pick up the next round. I'm using Pmags and have tried different ones, so I'm pretty sure that's not the problem. I've tried different gas blocks and that hasn't helped. I have tried different buffer springs, and so far the one that functions the best is a David Tubbs flat wire spring.The problem (I think) is in the ammo. I have a fair amount of 147 grain ammo, different manufacturers and the one it seems to work with the best is one called Perfecta, though its still not 100%. Today I fired some 180 grain Fusion ammo from Federal, and it fired flawlessly. I know what some will say, just use that ammo, but I want this firearm to eat what I give it..and I'd really like it to function well on 147 grain because I have a pile of it.. I was thinking about opening up the gas port in the barrel just a mite and using an adjustable gas block,,,but that is a little out of my experience, at least to date..So any insight into this would be appreciated.

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9 years 4 days ago #46856 by jtallen83
Replied by jtallen83 on topic AR10 Failure to Cycle
:welcome:

How many rounds fired?
Does it lock back on the last round at all and will it lock back manually? With the bolt all the way back how much space between it and the bolt catch?
What are you using for a buffer?
Can you tell if the gas block and gas port are lining up? Some makers build for the block to rest on the shoulder and some need some space to line up.
Is the gas tube in the correct position?
If all else fails you can open up the gas port, I had to on a 308 build myself. What size is the port now?
Most times these big bores need some hot ammo and lots of lube to break in then they start working fine, lots of lube like in a dripping wet BCG.

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9 years 4 days ago - 9 years 4 days ago #46858 by faawrenchbndr
Replied by faawrenchbndr on topic AR10 Failure to Cycle
147 grain ammo is known to scales this issue in AR10 and .308 pattern AR rifles. Stick with 168gr and above in factory loaded ammo.

If you want it to run on 147gr mil-surp ammo, the gas port is going to need to be opened up. I would suggest getting it to run on 147 and the opened port, then adding an adjustable gas block that would allow you to decrease the gas if you want to run heavier ammo later.
Last edit: 9 years 4 days ago by faawrenchbndr.

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9 years 3 days ago #46866 by Libertarian623
Replied by Libertarian623 on topic AR10 Failure to Cycle

jtallen83 wrote: :welcome:

How many rounds fired?

Most times these big bores need some hot ammo and lots of lube to break in then they start working fine, lots of lube like in a dripping wet BCG.

JT - You said it. It is as simple as that most the time, they should write it on the box.

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9 years 3 days ago #46874 by Charlie
Replied by Charlie on topic AR10 Failure to Cycle

faawrenchbndr wrote: 147 grain ammo is known to scales this issue in AR10 and .308 pattern AR rifles. Stick with 168gr and above in factory loaded ammo.


That right there.

My 10BF and 10BNMF would both short-cycle 168 gr when they were new. The only thing that fuctioned reliably was 180gr. Both have broken in now and will shoot 168, but our application is deer, so no reason to shoot the light stuff anyway.

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9 years 1 day ago - 9 years 1 day ago #46900 by mlotziii
Replied by mlotziii on topic AR10 Failure to Cycle

jtallen83 wrote: ...a dripping wet BCG.


What he said.
Last edit: 9 years 1 day ago by mlotziii.

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