Loose primers jamming an AR

January 07, 2018, 11:15 PM

quote:
Originally posted by cas:
It's generally accepted that crimped primers are to keep this from happening in machine-guns with questionable headspace. But reality is crimped primers (military and non) date back to the late 1800's, before full or semi auto weapons.

Hiram Maxim developed the first full auto recoil operated firearm in 1885.

But true that crimped primers in Mil-spec ammo isn't just about full autos........

January 08, 2018, 09:27 AM

Expert308

I had it happen a couple times back when I was learning about my then-new space gun. The guy who barreled it for me warned me about not making my handloads too hot because the throat was cut on the snug side. It didn't occur to me that commercial match ammo might also be too hot for it. So one day I'm out shooting and ran out of the handloads (77gr SMK), so I switched to a box of Hornady 75gr Match. After just a few rounds, the thing jammed solid. When I took it apart I found that a primer had popped out and wound up in the locking lugs. I picked up the brass and saw definite pressure signs on all of the Hornady cases. A couple thousand rounds later the throat had lengthened to the point that the Hornady ammo works fine, but with the new barrel it was just too hot - nothing wrong with the ammo, it was just that the throat was too short for it.

January 08, 2018, 10:16 AM

3/4Flap

I've had pierced primers in hot handloads but never a blown-out primer. Others have ID'd the various possible causes.

I don't shoot much factory ammo but as mentioned, there is a fairly wide range of case heat treatment and some dimensional variations that show up in handloading multiple times.

But primers coming out of factory ammo indicates clearly the need to never buy that brand of ammo again. It just so happens that a lost primer can be one of the toughest malfunctions to clear in an AR.

FWIW: I also note that primer crimping seems to vary tremendously in that some UNCRIMPED/UNstaked cases I've hand deprimed seem to take as much effort as the crimped-in ones. I'm not totally certain the crimping always has much significant effect on retaining primers. This seems to vary by lot and case within lots. Totally unscientific, but just something I've noticed.

**********************
53 Jesus said to them, “Very truly I tell you, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you.

Read Quod Apostolici Muneris (1878) LEO XIII. This Pope warned us about the Socialists before most folks knew what a Socialist was...

January 08, 2018, 01:35 PM

samnev

quote:
Originally posted by fritz:
quote:
Originally posted by Rustpot:
They were both with Freedom Munitions.

quote:
Originally posted by cas:
Primers should NEVER come out of the case. If they do, have have one of three things:

1. Over pressure loads, dangerously so.
2. A head space problem.
3. Reloaded brass than has been reloaded too many times, or over was loaded at one point.

Rustpot -- assuming your gun is properly built, I'd say you have an ammo problem.

+1 I agree with the above.

January 08, 2018, 02:13 PM

GySgt D

I've had it happen several times over the years, and quite recently, too.

The most recent culprit? I was shooting some late nineties-era reloads which had been tumbled clean using dirty crushed walnut tumbling media.

Things were fine during load development (back in the nineties), but when I cracked open the ammo can and shot some of it a couple months ago, nearly all of the ejected cases showed signs of excessive pressures- Many popped primers, flattened primers, and ejector marks.

Over the years, the filthy tumbling media film which had coated the inside of the cases had hardened.

I pulled the rest of the ammo, and the effort required to pull the bullets was sobering. Am very lucky I didn't blow the gun up.

Also sobering was the realization that this was my "emergency war reserve". Would have been truly sucky to have loaded up on that to repel the inevitable Peruvian amphibious invasion...

January 08, 2018, 03:10 PM

3/4Flap

quote:
Originally posted by GySgt D:
I've had it happen several times over the years, and quite recently, too.

The most recent culprit? I was shooting some late nineties-era reloads which had been tumbled clean using dirty crushed walnut tumbling media.

Things were fine during load development (back in the nineties), but when I cracked open the ammo can and shot some of it a couple months ago, nearly all of the ejected cases showed signs of excessive pressures- Many popped primers, flattened primers, and ejector marks.

Over the years, the filthy tumbling media film which had coated the inside of the cases had hardened.

I pulled the rest of the ammo, and the effort required to pull the bullets was sobering. Am very lucky I didn't blow the gun up.

Also sobering was the realization that this was my "emergency war reserve". Would have been truly sucky to have loaded up on that to repel the inevitable Peruvian amphibious invasion...

That's an interesting situation.

Dirty tumbling media also introduces grit/sand, etc into the case and can prematurely wear dies but also, as it is blown out the bore during firing, scratch the bore.

January 08, 2018, 06:30 PM

GySgt D

As an aside-

I shot perhaps a hundred or so rounds of this stuff before realizing what was occurring.

Erosion caused by the many popped primers ruined my bolt. The firing pin hole on the bolt face had enlarged. This caused subsequent (known good) fired ammunition to have pierced primers. The enlarged firing pin hole was acting like a cookie cutter, and tiny metal disks were punched out and entering the receiver and also the firing pin channel. After approx 150 rounds after cleaning, this caused the firing pin to lock up completely.

All because my 20 year younger self was too cheap/broke to change the tumbling media when it got nasty

January 09, 2018, 01:45 AM

CD228

quote:
Originally posted by GySgt D:
As an aside-

I shot perhaps a hundred or so rounds of this stuff before realizing what was occurring.

Erosion caused by the many popped primers ruined my bolt. The firing pin hole on the bolt face had enlarged. This caused subsequent (known good) fired ammunition to have pierced primers. The enlarged firing pin hole was acting like a cookie cutter, and tiny metal disks were punched out and entering the receiver and also the firing pin channel. After approx 150 rounds after cleaning, this caused the firing pin to lock up completely.

All because my 20 year younger self was too cheap/broke to change the tumbling media when it got nasty

Thanks for sharing that. I learned something from it. time to change the media.