Dead AR Trigger due to Blown Primers.

[JohnO]

A buddy's AR went down hard today. The Geissele trigger would not budge. The sear was unable to release the hammer.

I suspected the culprit was a primer and tried shaking and rapping the lower while inverted and manipulating the trigger what little bit it would move. No improvement!

I pushed out the pin and removed the hammer and still couldn't see a problem. Next removed the trigger and "Voila!” 2 blown primers stuck under the trigger. I suspect the quite liberal amount of lubrication in his lower prevented the primers from being dislodged from the earlier attempt.

This was a BCM KD4 Upper using Norma 62 gn. ammo.

This was a show stopper and a catastrophic malfunction if it had occurred under more serious circumstances.

Perhaps too much lubrication especially in unrequired areas can be detrimental. (Granted the primers shouldn't have blown and are the root of the problem.)

[Wake27]

What makes you think it has anything to do with lubrication?

I’ve had several between two different uppers, several years apart. There’s just enough space under a Geissele trigger for the primer to get lodged. I have zero reason to think that lube contributed in any way but it definitely can bring the whole gun down. More than once, the only way to remove it was with a multi tool. I don’t remember if I had to remove the FCG or not at any point.

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[Suvorov]

I have heard this happening before.

Was the trigger slathered in grease causing the two blown primers to stick? What kind of ammo was he running?

[ST911]

Dropped primers are individual chamber/ammo issues or compatibility, not lube. Used to see it more often before chambers got better or people started gauging and reaming them. Some trigger designs are more susceptible, whole primers may shake or drop out. Primer pieces/remnants tend to get stuck places. NBD but bears noting and avoiding - esp in a life support gun.

[JohnO]

What makes you think it has anything to do with lubrication?

Had there been less or no oil in the base of the lower I think the primers would have been more likely to be coerced out without the need to remove the FCG. It was swampy down there.

[Pnut]

Had this happen with an unusually hot batch of Fed XM193. The blown primer lodged in between the sear and hammer, and wouldn’t budge without removing the trigger assembly. My gun wasn’t over lubed.

[Olim9]

I've seen blown primers make someone's rifle go down hard using Hornady Frontier ammo. I was even seeing primers seperating mid flight from the brass. This was also when I saw the same thing occur on someone on social media, Hornady brass has loose primer pockers to my understanding.

[Clusterfrack]

I’ve seen this, and had it happen. As @Wake27 posted, most of the stoppages are fixable with a tool. This is one reason I prefer open triggers over drop in modules.

Hornady brass sucks, but I’ve never seen blown primers in quality factory ammo unless something else was going on. Wet ammo can cause high pressures, and blow primers.

[GJM]

Would a cassette style trigger prevent this?

[Clusterfrack]

Would a cassette style trigger prevent this?

In my experience, no. But cassette triggers make it harder to clear.