AR15 Double Fire/ Slam Firing

An AR-15 firing pin cannot get stuck in the foreword position unless it is broke in two.

When the bolt carrier is blown back off the bolt to unlock it, the firing pin is mechanically retracted and is shorter then the bolt body.

The only time it is able to reach a primer is when the bolt is telescoped back inside the carrier and fully locked in the barrel extension.

Doubling can be caused by only one of three things:
1. Defective trigger / disconnecter.
2. Soft or too sensitive primers getting set off just as the bolt is fully locked shut and the firing pin is able to fly foreword and hit it.
3. A very light trigger, combined with a relaxed hold on the gun, allowing the gun to "bump fire" against your trigger finger.

rc.

I had an AR go full auto when one of the FCG pins backed out (can't remember which one for sure, but I think it was the trigger). Didn't dump the whole mag, just kept firing as long as the trigger was pulled back. Interestingly, it did it with a 22lr adapter and with the 5.56 BCG. That problem would seem easy to see, but someone else had to show it to me because I was so flustered by the problem.

Riddle

My BIL has an older AR that will double fire when he, and he alone shoots it. 3 other shooters (myself included) could not induce his issue trying every trigger handling trick in the book. He would shoot it, double fire. We would shoot it, 1 pull, 1 fire. I even tried the famous artillery hold we used to shoot powerful springer air rifles, with no success duplicating his issue.

Obviously a bump-fire issue, with his trigger or hold technique, but he has tried every trigger drill out there, without success.

He's going to replace the trigger-group, and go from there. I'm suspecting worn components and holding too loosely, but it should only fire once, no matter how held.

Very odd, that 3 of us couldn't duplicate his issue, and we all fired it many times.

The rifle is defective, that much we all know.

Wow. Such a magnificent rifle, the Armalite.

I am so Glad for the spring loaded firing pin and the FCG on my SIG556 and my PTR91. No issues like this at all.

Yep.

Reloads with soft primers may do that from what I understand. Federals, and some Winchesters have that reputation.

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If youre using reloads, especially with Winchester primers, I wouldnt get to concerned. Just switch out the Winchesters for CCI.

I got a couple of thousand Winchester small rifle primers from a buddy, and figured Id burn them up, so I loaded up a bunch for my one Armalite. I usually use CCI, and never had any issues with slamfires with my reloads using them. With the Winchesters, from the very first mag, I was getting doubles and triples with just about every pull of the trigger. Switch out the mag for one with CCI's, and the problem immediately stopped.

I've seen brand new SIG M400 AR15s doubling because of the trigger pins walking out. I'm not sure what happens when the pins start walking out but could be something similar.

FIVETWOSEVEN said:

I've seen brand new SIG M400 AR15s doubling because of the trigger pins walking out. I'm not sure what happens when the pins start walking out but could be something similar.

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That's why I always use KNS Anti-Rotation pins in all my ARs.

Ounce of prevention...

stubbicatt said:

Wow. Such a magnificent rifle, the Armalite.

I am so Glad for the spring loaded firing pin and the FCG on my SIG556 and my PTR91. No issues like this at all.

Yep.

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Firing pin spring is standard on the ArmaLite AR-10. It is not needed on the AR15.