Fired case from out of battery AR-15?

[Shrinkmd]

I think my AR fired out of battery, I see there is a light strike on that primer, and the case has a very unique shape. I somehow missed this when I was putting the fired cases away, and I noticed this when I was running them through the annealer. Does this look like a case fired out of battery?

 

[AJC1]

Isn't Aztec the analysis mode that eats a case to give you a setting?

 

[Shrinkmd]

I totally changed the name and content of my post, I was emailing with Alex from AMP annealing and I totally remembered my rifle doubling, and this must be the case. How I didn't notice the neck blown out...well..it was very cold in TX that morning! He thought I annealed a primed case, but I know that didn't happen, my ears would still be ringing, all I hears was the jazz station WBGO over the bluetooth speaker...

 

[dredd]

Ahhhhhh..... That makes more sense.

I have run hundreds & hundreds of cases (by hand) and sacrificed dozens. Your case just didn't make any sense at all to me.

I couldn't figure out how the AMP would make it look like that.

Thanks for the clarification.

 

[Shrinkmd]

Now I need to figure out what's wrong with my rifle, although I think some of my primers might have been a little high, and wondering if it was a slam fire. I think my swager on the 1050 wasn't opening everything up all the way, and then I readjusted my primer punch depth as well.

Although now that I think of it, these are those new Winchester #41 primers that are out. I don't remember my rifle every having double or slamfire before.

The trigger is a LaRue double stage which has probably 2k on it, I haven't messed with any springs or done anything to it, so it's possible it's acting up?

 

[Metal God]

Out of battery sounds as good as anything to me . Maybe a low charge not enough to expand the case fully to seal the chamber resulting in premature extraction blowing out the neck while still under pressure but would think that would cause extraction/ejection issues .

I only stress relieve my auto loader brass when I anneal . Usually in the 750* area rather then fully annealed . I get poor/low bullet hold when AR cases are annealed to AMP dead soft type annealing . Maybe you had some bullet set back on chambering causing poor ignition resulting in something similar as a low charge .

It looks like the case head was up against the bolt face because it looks like you may have had some of the cup flow back into the firing pin hole . What ever happened it appears your firing pin dimple in the primer was blown back flat and if the head wasn’t against the bolt face the primer should have been blown free .

IDK , I too have never seen a case like that , just some thoughts I figured Id throw out there . .

 

[Enfielder]

Looks like an unsupported detonation of a brass case to me. Check your firing pin/channel for grime or burrs. the primer flowed rearward from being unsupported as well.

 

[Yankee1986]

I am not an expert but I know I've read that due to the design of how the firing pin works it is impossible for an AR15 to fire out of battery.

I also know virtually nothing is failsafe and I'm sure I'll get corrected if wrong.

 

[Shrinkmd]

Thanks for the advice, I will be checking the bolt carefully as I'm cleaning it later. I will also adjust the swager and primer punch on the Dillon to make sure those puppies are seating all the way, I know I've felt one or two that might have been a touch high, but never had a problem before.

I am considering switching to Starline and retiring my old PPU brass and mixed range pickup...I'm a better shooter now, so it's time for higher quality brass and bullets

 

[Walkalong]

Isn't Aztec the analysis mode that eats a case to give you a setting?

Yes, but it doesn't do that to them, just gets them too hot.

 

[Walkalong]

Looks like a round fired in a long chamber like the wrong caliber, but that's not the case here.

 

[chevrofreak]

An AR-15 can't fire out of battery unless there is something wrong with the bolt face or the firing pin was stuck.

And it would have disassembled your firearm.

 

[GeoDudeFlorida]

I totally changed the name and content of my post, I was emailing with Alex from AMP annealing and I totally remembered my rifle doubling, and this must be the case. How I didn't notice the neck blown out...well..it was very cold in TX that morning! He thought I annealed a primed case, but I know that didn't happen, my ears would still be ringing, all I hears was the jazz station WBGO over the bluetooth speaker...

I was wondering about that primer, too. OOBE makes more sense.

 

[Shrinkmd]

Yes, fortunately the firearm was not "disassembled" by what occurred, and it actually shot a very nice group afterward. That case is definitely a keeper, kind of like those pictures of disassembled revolver cylinders from double charges, but without the firearm damage.

I will be examining that firing pin and the bolt very carefully...

 

[BreechFace]

Not possible on an AR15

Once the bolt carrier starts moving back to unlock the bolt from the barrel extension the firing pin is no longer long enough to reach the bolt face and contact the primer.

Slam fires can occur with a proud primer or out of spec firing pin. But they would occur in battery.

So for this to occur one would have to have an out of spec bolt lugs, barrel extension, or too long firing pin. An in spec AR15 this is an impossiblity.

 

[Shrinkmd]

So assuming the primer was a bit proud, and the gun fired in battery, is that still consistent with that bizarre blown out case?

 

[Nature Boy]

Could you have picked up someone else’s case at the range thinking it was your?

I can’t come up with a scenario where a .223 chambered rifle would produce a case that looks like that

 

[Shrinkmd]

It's definitely my case, same headstamp, and it was in my brass catcher... not a lot of PPU 07 floating around

 

[BreechFace]

So assuming the primer was a bit proud, and the gun fired in battery, is that still consistent with that bizarre blown out case?

Not unless your chamber looks like that, and then all your cases would look like that.

 

[Varminterror]

This is what I’ve seen from slam fires in AR’s. As @BreechFace mentions, the failure mode for slamfire in an AR means “bang” happens when the round is nearly fully supported in the chamber, but when this happens while the bolt is not fully locked, the action is blown back open while the chamber pressure is too high, allowing the brass to move without sticking to the chamber wall, and self-extracting during sufficient pressure to blow out the shoulder.

So technically, it’s still an OOBD, as the bolt wasn’t fully locked into battery, but rather, you had JUST ENOUGH chamber support during the pressure cycle to avoid blowing apart the brass, and the mag…

 

[BreechFace]

@Varminterror You’re saying that the there is enough firing pin protrusion when the bolt lugs are clear of the barrel extension?

I’ve never been witness to an OOB in an AR15, and with knowing how the lockup occurs I can’t understand how there is an in between on being fully seated and not.

 

[Varminterror]

@Varminterror You’re saying that the there is enough firing pin protrusion when the bolt lugs are clear of the barrel extension?

I’ve never been witness to an OOB in an AR15, and with knowing how the lockup occurs I can’t understand how there is an in between on being fully seated and not.

Only other way it happens is broken lugs, so there’s no support for the lugs to temporarily bear - and seize - against during the pressure cycle.

But the OP mentions the rifle doubling, which does have multiple root causes, but only one of which results in THIS kind of blown out case.

 

[N555]

That's awesome. I figured if an ar15 lit one off out of battery it would blow up, or at least break something.
Seems like you didn't even know it happened.
There not supposed to be able to do that.
My guess, firing pin too long?

 

[Varminterror]

If they truly fire out of battery, sufficiently unsupported, it’s really uneventful. They blow the bottom out of the mag, brass shrapnel out of the port, bending the top rounds in the mag and ruining the box, so it’s certainly exciting, but it’s overall underwhelming for what we might expect to happen.

Yet another reason to use an AFG instead of gripping the magwell when operating operationally - no risk of physical damage, but that “THUMP” in the pinky would certainly be alarming.

 

[Shrinkmd]

Thanks for all the great info! Unless the original BCM firing pin has been eating too much and not hitting the gym, it shouldn't be growing any. I think reloader error and those new Winchester primers might be the culprit, but since I bought a few of them, I will be double checking the swager, primer seat, and that bolt/firing pin!

Let's hope no more interesting cases in the future!