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Author Topic: Odd AR malfunction  (Read 259 times)


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Odd AR malfunction
« on: September 20, 2017, 11:18:40 am »
So I took one of my ARs to the range to sight in a new red dot.  Got the red dot sighted in without much drama, but had a new to me malfunction.  Every so often the gun would cycle, pick up the next round and mostly chamber it.  The extracted round would hang up with the base of the round wedged against the front of the ejection port, like a handgun stovepipe.  This happened with two different brands of 55 grain ammo and three different types of magazines.  The rifle is a Stag left-handed upper, 16" barrel, on a small company lower, and aside from the red dot, the only change I've made from previous trips was I put a 30 caliber silencer on it instead of a 223 caliber silencer.

Any ideas?


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Re: Odd AR malfunction
« Reply #1 on: September 20, 2017, 01:20:14 pm »
Sounds like it short stroking. Did you take the suppressor back off to see if the issues go away? How often are you cleaning the rifle?

6.5 Gunner

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Re: Odd AR malfunction
« Reply #2 on: September 20, 2017, 02:07:06 pm »
Check the gas block to see if it's loose.


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Re: Odd AR malfunction
« Reply #3 on: September 21, 2017, 02:51:50 am »
Try shooting with the old suppressor and without a suppressor to see if there is any difference.


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Re: Odd AR malfunction
« Reply #4 on: September 21, 2017, 10:35:32 am »
I would also suspect the gas block, maybe it's slipped somewhat out of alignment with the barrel port.

I've had this specific problem with a self-assembled Upper, and the cause was the gas block alignment; it had slipped. I measured the block internally to establish where the hole should line up, then measured the barrel from the shoulder to the barrel port. Te difference is the amount of space that should exist between the rear of the block and the shoulder.

A 30 caliber suppressor might produce less port pressure, but I really don't think that's the problem, unless it's complicated by gas block slippage.

The first thing I'd do is try the rifle without the suppressor. If the problem remains, I think that more or less confirms gas block slippage.

« Last Edit: September 21, 2017, 10:56:59 am by JarheadAZ »
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Re: Odd AR malfunction
« Reply #5 on: September 21, 2017, 10:47:29 am »
Had a buddy with the same problem, turned out to be a primer stuck on the gas block.  Look for obstructions, run a pipe cleaner down through the gas block.  If you can find one, take an old wire coat hanger straighten it out and run it down the gas tube as well.  Any kind of obstruction will cause short stroking.  Also, pull the bolt apart, check the ejector stud spring, it may be broken.


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Re: Odd AR malfunction
« Reply #6 on: September 24, 2017, 09:31:28 pm »
If it is picking up the next round this is not short stroking. This is failure to eject. Likely causes are bad ejector function and/or bolt velocity too high.
What buffer are you using? I'd use an H3 on a 16" carbine with suppressor. I'd also remove the ejector and clean out the ejector channel, and replace the ejector spring. Measure your action spring while you are at it too.

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Re: Odd AR malfunction
« Reply #7 on: October 08, 2017, 05:25:53 pm »
Sounds like the bolt is dry. IMPO the first thing is always do cheap first.. Take apart, clean and look for obstructions. Lube up everything and reassemble.  It might be something stupid like a pin not seated correctly.
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