Dead AR Trigger due to Blown Primers.

[Wake27]

Adding the following.

There was someone at the training event who told my friend that his gun was overgassed and that caused the primers to blow out. The advice included a recommendation of modifying the gun either with an adjustable gas block or an adjustable bolt carrier. I stayed out of that conversation. Later my friend contacted me and asked what I thought he should do.

I started with "don't monkey with the gun! Two blown primers do not equal a gun in need of modification/gas regulation." I told him you don't throw the baby out with the bathwater without knowing the actual cause.

My friend told me he went online and found only positive reviews of the Norma 62 gn. ammo he was using. I told him the typical guy writing a review is no different than the typical gun owner. They don't shoot enough to have a worthwhile opinion!

We are both attending a high round count carbine class next month, he doesn't want the gun going down like that again. My friend has decided he is going to the class with a different upper, a 13.7" pinned & welded to 16".

AFAIK, the only real way to easily ID whether it is the gun or ammo is to try another one and see what happens. Obviously if it happens in the 13.7 with the same ammo, it’s ammo related. My Criterion barrel popped MEN primers the vast majority of the time, but it did pop an Igman .223 once or twice as well. I’ve also run the MEN is a number of other uppers without issue, so pretty easy to say that it was something wrong with the gun.

While that’s all fairly obvious, I’m not aware of anyone that considers blown primers a symptom of simple overgassing. Common overgassing is just excessive felt recoil and fouling. Excessive overgassing leads the bolt to out-running the magazine, causing malfunctions. Overgassing can be solved a few ways, my preferred would be a BRT gas tube and/or LMT E-carrier before anything adjustable.

Blown primers are the next step up and a over-pressurization issue. If it can be identified as the upper, it needs to go back to the manufacturer to probably get the barrel replaced.


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[Yute]

A data point I found re: milspec trigger vs cassette triggers with popped primers:
https://www.youtube.com/watch?v=WkLvREGFbnM

I am curious how the KE Arms Rekluse triggers would perform; they are as sealed as you can get.

[MTP]

Blown primers stuck in the trigger components are definitely bad, and some trigger designs might mitigate that.

But lets not forget that blown primers can take a gun down even if they land in other places:

I had one of my own Colt A4s go down hard because of blown primers stuck behind the lugs of the barrel extension. Bolt doesnt go into battery, just one iteration of tap-rack jams up the bolt and the (now mangled) primer nicely. Bolt doesnt budge, cant take the rifle apart because the bolt is partially OOB. The fix takes 10 minutes and some tools depending on how bad and where exactly the primer is stuck.

[Jim Watson]

It isn't just ARs.
A battery cup primer down in the trigger group of a Model 12 pump will shut down the shotgunning, too.

But the strangest malfunction I have seen with a shotgun was the O/U that would not close. We eventually tracked it down to one shot pellet under the extractor.

[JRB]

Adding the following.

There was someone at the training event who told my friend that his gun was overgassed and that caused the primers to blow out. The advice included a recommendation of modifying the gun either with an adjustable gas block or an adjustable bolt carrier. I stayed out of that conversation. Later my friend contacted me and asked what I thought he should do.

I started with "don't monkey with the gun! Two blown primers do not equal a gun in need of modification/gas regulation." I told him you don't throw the baby out with the bathwater without knowing the actual cause.

My friend told me he went online and found only positive reviews of the Norma 62 gn. ammo he was using. I told him the typical guy writing a review is no different than the typical gun owner. They don't shoot enough to have a worthwhile opinion!

We are both attending a high round count carbine class next month, he doesn't want the gun going down like that again. My friend has decided he is going to the class with a different upper, a 13.7" pinned & welded to 16".

Another thing to consider, is the BCM KD4 uppers were designed exclusively to use the Black Hills 77gr 5.56. Everything including the chamber specs and rifling twist rate is intended to optimize performance with that exact Black Hills 77gr ammo. I would expect that to introduce 'quirks' if running any other kind of ammo.

[Clusterfrack]

Blown primers stuck in the trigger components are definitely bad, and some trigger designs might mitigate that.

But lets not forget that blown primers can take a gun down even if they land in other places:

I had one of my own Colt A4s go down hard because of blown primers stuck behind the lugs of the barrel extension. Bolt doesnt go into battery, just one iteration of tap-rack jams up the bolt and the (now mangled) primer nicely. Bolt doesnt budge, cant take the rifle apart because the bolt is partially OOB. The fix takes 10 minutes and some tools depending on how bad and where exactly the primer is stuck.

Yep. I had a blown primer jammed between the carrier and receiver. (Reloaded ammo).

[Wake27]

Oh yeah, forgot about that one. I had one in the upper as well, I can’t remember where exactly but it definitely prevented the bolt and next round from seating correctly.


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[Cacafuego]

I had one get stuck in the gas key, all the way down in. Took me forever to figure out what was wrong

[Clusterfrack]

I had one get stuck in the gas key, all the way down in. Took me forever to figure out what was wrong

LOLOL!

[TGS]

Blown primers stuck in the trigger components are definitely bad, and some trigger designs might mitigate that.

But lets not forget that blown primers can take a gun down even if they land in other places:

Yep. I had a blown primer jammed between the carrier and receiver. (Reloaded ammo).

Just to dogpile:

I had a primer blow out in a Daniel Defense shooting Prvi Partizan .223 75gr OTM. Got lodged in the BCGs cam pin channel.

Took a mallet and brass punch to get the BCG out.