Out of battery question w/pictures

[Jon.]

So had an OOB, I wasn't shooting it but I watched it. Blew the magazine out and big puff of smoke out of the ejection port. No injuries or anything, but some damage to the gun.

What I'm unsure of is why it happened. The firing pin sheared off, but I don't know if that was before or after. My only and uneducated guess is the hammer sheared off and may have gotten caught behind the firing pin? The firing pin in this bolt does have a spring in it, but disassembling it there was nothing wrong with, or any other parts caught in there that may have. No other damage. The brass is jammed into the locking lug area outside the chamber. All handloads, probably the the thousandth of the same load through it, chances of a messed up load are negligible, loaded with a chargemaster and varget, not much extra space in the cases to make mistakes. No I don't load pistol powders. Not a squib, the prior round hit the gong quite clearly. Triggertech trigger also.

I have tons of experience with AR15s but this is something quite new to see.

I'd guess about 2000 rounds max through this gun since I bought it, and I'm the only and probably forever only owner. #### you Liberals.

Any ideas?

 

[call2arms]

So I thought we were not to be using these evil death machines.

 

[Jon.]

So I thought we were not to be using these evil death machines.

What do you mean, maybe this happened 13 months ago, I threw it in the safe and I've just gotten around to asking about it?

 

[Bratwurst]

Unsure, my guess is you could kick out the old brass then re-assemble and function test the firearm.

Listening to the trigger reset might provides clues.

You could also try swapping the trigger out.

Maybe swap bolt carrier groups too?

 

[Blastattack]

None of what you posted makes any sense. OOBs don’t result in an intact case head. There are only two ways for an OOB to occur in an AR15; the firing pin breaks and the tip seizes in the bolt head, or a reloading error results in a high primer. I can’t fathom what happened, because I can’t see how it could have happened, or how it could have done so little damage.

 

[deadman]

Ok, I'm certainly no expert on this, but I'll throw in my hat. Does the design of the bolt/firing pin interface not prevent an out of battery fire? The pin should be retracted with the motion of the bolt right? You mentioned the firing pin sheared off. The design of the AR bolt retracts the fp and can't allow firing out of battery, but if the pin broke (previous shot), you could have had a return to battery strike if things got jammed up with the broken piece.

Or maybe a proud primer? I'm spitballing here, as I said I'm no expert.

Blastattack beat me, and said it better.

 

[Jon.]

None of what you posted makes any sense. OOBs don’t result in an intact case head. There are only two ways for an OOB to occur in an AR15; the firing pin breaks and the tip seizes in the bolt head, or a reloading error results in a high primer. I can’t fathom what happened, because I can’t see how it could have happened, or how it could have done so little damage.

Yeah it doesn’t make sense to me too. But bolt wasn’t locked up when it went off. Firing pin bolt head heck the whole bcg is just fine. It blew out the side of the ejection port and blew the magazine down and out. Mag follower broke in half and the baseplate was not found. A bit of powder burn on the guys hand but the gun performed flawlessly to save itself and the shooter. The case head is about the only part left, it’s split open like a looney tunes gun barrel inside the bolt head lockup space. I need to buy a dowel or stronger rod to knock it out. I hand seat primers and toss anything that’s loose as I get all the 308 brass I’d ever want from work.

Can’t assemble and try it, the hammer is sheared off. That’s why I’m wondering if it’s possible it could have stuck in the bcg and held the firing pin forward just enough. It’s why I posted here to ask for ideas or help. I watched it happen and disassembled it after, it was very much out of battery.

 

[Jon.]

Ok, I'm certainly no expert on this, but I'll throw in my hat. Does the design of the bolt/firing pin interface not prevent an out of battery fire? The pin should be retracted with the motion of the bolt right? You mentioned the firing pin sheared off. The design of the AR bolt retracts the fp and can't allow firing out of battery, but if the pin broke (previous shot), you could have had a return to battery strike if things got jammed up with the broken piece.

Or maybe a proud primer? I'm spitballing here, as I said I'm no expert.

Blastattack beat me, and said it better.

I’m open to ideas as I’ve never seen this type of failure before. No judgement zone.

 

[Jon.]

Unsure, my guess is you could kick out the old brass then re-assemble and function test the firearm.

Listening to the trigger reset might provides clues.

You could also try swapping the trigger out.

Maybe swap bolt carrier groups too?

Tossed the old trigger. The bcl first run weren’t very good. This one is dead now.

Don’t really want to buy a new bcg for a gun I’m not allowed/supposed to shoot either.

 

[coyoteshooter]

So had an OOB, I wasn't shooting it but I watched it. Blew the magazine out and big puff of smoke out of the ejection port. No injuries or anything, but some damage to the gun.

What I'm unsure of is why it happened. The firing pin sheared off, but I don't know if that was before or after. My only and uneducated guess is the hammer sheared off and may have gotten caught behind the firing pin? The firing pin in this bolt does have a spring in it, but disassembling it there was nothing wrong with, or any other parts caught in there that may have. No other damage. The brass is jammed into the locking lug area outside the chamber. All handloads, probably the the thousandth of the same load through it, chances of a messed up load are negligible, loaded with a chargemaster and varget, not much extra space in the cases to make mistakes. No I don't load pistol powders. Not a squib, the prior round hit the gong quite clearly. Triggertech trigger also.

I have tons of experience with AR15s but this is something quite new to see.

I'd guess about 2000 rounds max through this gun since I bought it, and I'm the only and probably forever only owner. #### you Liberals.

Any ideas?

my idea is this the firing pin broke on the first shot ....the case rear motion kept front portion in bolt during extraction ...then when next round is picked up to go in battery there is no guarantee the front potion of the broken pin fell out and has rotated a few degrees in all the motion ...now there is also no guarantee the brake in the pin was a nice clean 90 degree one so now we try to go into battery with an un aligned break ....that is broken part end does not mate with rest of pin and now we have a longer firing pin showing out the bolt face and headed for battery like on a sten gun but with real pressure round.........look at the pin break in the bolt if its not re hammered by the rear pounding of front portion of pin during the blow up.....ask some old guy like me about the winchester mod 100.....the event started with a broken firing pin and you were un lucky enough to have it not fall clear see how far in on the pin the brake came ,,,,, the tail may be told.....im not sure what your type of pin looks like but i have seen this in a mod 100 in 308 ....AND a mod 1895 marlin in 3856 so look for clues and good luck don

 

[redshooter]

Well clearly it went bang out of battery, and since there's only so many ways that can happen, broken pin first, high primer second, and I suppose the right piece of debris mixed with bad luck. Glad all digits and peepers are still in place.

 

[scourge18a]

I would guess a proud primer if you are hand loading.
The primer can get smacked by the bolt lugs on the way into the chamber.
Or maybe the firing pin was broken first.

 

[phoenix]

Broken Firing pin maybe combined with a loose primer pocket.... I have had a similar OoB with a factory Colt rifle, similar results.. be thankful you were not badly injured.

 

[Jon.]

Firing pin is in perfect shape. That was my first thought. Cam pin bolt head gas rings cotter pin every part of the carrier group is fine.

I’m assuming it had to be either the broken hammer or my primer issue at this point.

 

[phoenix]

don’t think broken hammer can cause OoB, as the cam path doesn’t let a complete firing pin protrude enough to hit a primer until it’s in battery.... had to be something there to hit the primer.

 

[B]

That would be one of the least impressive OOB I have seen, especially considering its .223. You are definitely lucky as far as the end result.

 

[REKO]

looks like the wear inside your upper let your cam pin move early allowing the bolt to close prematurely, thus presenting the firing pin to the round as it was being loaded. Now what caused the cam pin to wear down your upper like that? no idea.

 

[Jon.]

That would be one of the least impressive OOB I have seen, especially considering its .223. You are definitely lucky as far as the end result.

.308

The way the brass is petaled out like a flower shows it was only partly chambered. There is the ejector mark on the brass but it’s proud not dimpled in.

 

[Jon.]

looks like the wear inside your upper let your cam pin move early allowing the bolt to close prematurely, thus presenting the firing pin to the round as it was being loaded. Now what caused the cam pin to wear down your upper like that? no idea.

That’s part of my mystery also. Was that from before or was it from the event, or me mortaring the action to get the bcg out.

 

[B]

.308

Gotcha, all I saw was AR-15 in the post, I can't quite read the headstamp on my phone. Just reinforces what I said. I had what I assume was an OOB or maybe a bad round in an X-95 and the rifle was annihilated.