AR15 trigger malfunction, firing double+ rnds:)

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Brianma65

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Hey , just wondering what are the common causes of a AR15, semi auto, doing 5,6,7 rnd bursts.

I’m guessing a trigger issue?

Sequence would be as follows rnd 1 no reset.
Pull back on charging handle and watch trigger reset.( almost halfway back and trigger resets)

Rnd,2,3,4,5,6,7 full auto.

Then no reset.

Pull back CH and reset trigger.

Rnd 8,9 double tap.

Reset with CH again and fire last shot

So again, this sound like a trigger issue?

Maybe set up to light?

Trigger is anew milspec trigger that came in a Luther LPK.
It has a very light pull

Edited:
This is not happening to me.
Just curious as I watched a YouTube vid , about this issue.
My buddy is having same issues
 
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mb9 said:
Try swapping each part one at a time until the culprit is found. Interesting symptoms.
Click to expand...
ya, this ones strange. I’ve experience double taps, but not 8 in a row:)

One mag he fired it was , rnd 1 no trigger reset, pull back CH, halfway to reset trigger, then 8 rnd burst, Then no trigger rest for last rnd.
 
The only time I've ever had an AR string on me was when one of the trigger pins moved a little to the side and the trigger parts became misaligned. Was a used rifle, previous owner must have been messing around where he shouldn't have been. Turns out the spring was not in the groove on the pin which allowed it to slide. I removed the trigger and put it back together properly and it never had issues again.

I would take it apart and be very careful putting it back together to make sure everything is right. If that doesn't fix it either replace it or take it to a gunsmith for troubleshooting.
I know you said it is a new trigger but it is possible something is out of spec so don't rule out that your trigger is no good.
 
cr5 said:
The only time I've ever had an AR string on me was when one of the trigger pins moved a little to the side and the trigger parts became misaligned. Was a used rifle, previous owner must have been messing around where he shouldn't have been. Turns out the spring was not in the groove on the pin which allowed it to slide. I removed the trigger and put it back together properly and it never had issues again.

I would take it apart and be very careful putting it back together to make sure everything is right. If that doesn't fix it either replace it or take it to a gunsmith for troubleshooting.
I know you said it is a new trigger but it is possible something is out of spec so don't rule out that your trigger is no good.
Click to expand...

This x 2
 
I’ll take a look at his disconnect spring.
He said he had two different springs.
One was about a 1/4 inch long,
The other was about 3/8 inch long.
He used the shorter one.
 
Canada tail said:
It is the sear. Get a new one.
Click to expand...

No part called "sear" in FCG of semi auto AR15 . There is the sear surface where in mil spec style FCG of the hammer and the front of the trigger . On many aftermarket triggers this is in a different location

TriggerMacro-11_zpsc040c567.jpg


If there is something seriously wrong with this sear surface hammer would not be held back

When hammer follows through and multiple rounds fired , the disconnector is not catching / holding back the hammer until the the trigger is reset ( ie you let go of the trigger )

When dry firing after charging BCG ( so reset hammer ) you can hear the click when you release trigger. This is the hammer's sear surface (#### notch ) engaging with the trigger sear surface ( clearly seen in pick above ) after disconnector

releases hammer .

As already mentioned , if the disconnector is not catching hammer, which is what your situation is , hammer will follow through and striker firing pin again. Often this will result in light primer strike .

BTW this the purpose of the auto sear in select fire FCG . It holds back the hammer until BCG is almost in battery ( tripped by the bottom of the M16 carrier...which is why it has more material than semi carrier ...as it passes by ) This is to prevent hammer follow through were hammer rides the carrier back. The disconnector in auto cannot engage the hammer since the auto position of the selector holds it back. Disconnector only engages once trigger is released in auto

Since your FCG is new, I am assuming the disconnector is not worn/ damaged but rather spring is not installed correctly or disconnector binding
 
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I had a friend that had that happen once and it was a milsepc trigger group that was the problem. Can’t remember where he got it from. The hammer was extremely hard to lock back. It wouldn’t lock back after the first round was fired and just kept going 2-5 times. New FCG fixed it.
 
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