Out Of Battery Detonation AR

[writerman]

I keep thinking through possibilities but they all circle back to the reloading bench.
Please give us more info on reloading tools (press, powder measure, etc) and on the components used (powder, primer, brass, bullet & weight). Example: a shooter blew up his 6.5 Creedmoor bolt gun. It was not repairable but the builder kindly told him he would build another free of charge. Two months later he blew the magazine and ejector out of that one. While I wasn't there when the first problem arose I was for this instance. He was adamant he didn't do anything wrong at the reloading bench but I did get him to promise to pull bullets on a couple. He called me and said he was using an Autothrow and had forgotten to clear the powder measure's metering chamber of H4895 before going to what he thought was 41 grains of H4350 for the Creedmoor.

More pictures please
View attachment 1542157
Brass flowed deep into ejector hole?
Flat primer still below flush with crater?
Extractor pulled the case rim off and case blew out?
Bolt is trash, right? Broken lugs?
Too much gas and over pressure?
Caliber, headstamp, and gas port size?
Missed the .223 in the first post.
Looks like some of the case damage was from pulling the blown case out.

 

[writerman]

I guess he figured it out but won't reply.

Sorry. I checked the 'email replys' but got none. I posted another pic.

 

[writerman]

Sorry. I checked 'email me replies' and when I got none, I thought there weren't any. I believe the brass was PAC .223 Remington, loaded with H335 23.5 grains, OAL 2.245. Primer CCI. None of the other spent rounds had any indication of cratered primer. I still need to know how this happened. It was not a case of the bolt slamming forward and detonating the round. I pulled the trigger and it went boom. Split the magazine open, curled the bolt back/split it, cracked the upper and lower, popped out all the loaded bullets, and cracked the barrel extention right in half.

 

[writerman]

What brass is that? The web looks quite thin.

PAC

 

[writerman]

That's about the most severe ejector mark I've ever seen.
More pictures of the case would be interesting.
Caliber and headstamp?

223 PAC posted another pic.

 

[writerman]

About all anyone can do is guess. A high primer can do that. A trigger without enough sear engagement so the hammer follows the bolt can do that. A stuck firing pin could do that.

It was not a slam fire, no squibb. It was pull the trigger, bam!

 

[writerman]

My thoughts are over pressure, how,why, what I dunno. Makes little difference if a body has been loading 50 years or 50 minutes, we are human and prone to err at times.

All the other rounds loaded at the same time showed no signs of overpressure. I posted another pic of the back of the round, that primer is not cratered either.

 

[writerman]

That's an over pressure failure, primer is still in place.

But over pressure from what cause? All the other rounds were fine, loaded at the same time. I really need to know what happened, so it doesn't happen again. Gunsmith said 'shoot long enough, it's bound to happen.' Ouch.

 

[writerman]

I’ve not experienced an out of battery firing on an AR platform. What convinced you that this was the cause?

What else could it be? Fifty rounds fine, at fifty one, pulled the trigger and bam! Not a case of squibb load or overloading, or slam fire.

 

[writerman]

Going to need more pictures and the load you were shooting to help determine what happened.

Posted that info. Thanks.

 

[writerman]

No, so some of my comments may not be accurate. But I have fired in excess of 20K rounds through AR's. Looking at the primer the firing pin indentation is seriously cratered and the primer pocket looks really large. Both of those seem to indicate very high pressure. But since I don't know the case damage from OOB firing, I don't know how much to attribute to that. The case head would have been encased in the bolt with the weak point being the extractor.

So to try and understand what might have caused it:
- how do you set up your sizing die?
- how much do you set back your shoulder?
- were all 100 the same brass lot?
- have you ever had an issue with the bolt not closing completely on any AR rounds before?
- during your 50 years of shooting, were you reloading during this time?
- what powder and charge were you using in combination of bullet and seating depth?

I'm just trying to understand contributing factors as it might not be a single cause. If the bullet was driven back into the case when chambering, it could have reduced the case volume and absorbed bolt closing force to avoid full battery.

I used to read about blown primers in AR's and until one time never experienced one. I was shooting a 204 Ruger upper and one round was 200 fps faster than the rest. Same headstamp but not brass lot. When I checked case water capacity of the case it turns out to be considerable lower capacity. Evidentially a much older Hornady case in with newer production. Everything had been just fine, but when your case capacity is over 10% less, it leads to excessive pressure.

I have been reloading for about seven years. Hundreds upon hundreds of rounds. It was not a case of overloading because all the other rounds from the same bag were fine. No signs of overpressure. OAL 2.245 23.5 grains of H3353, CCI primer 55 gr. FMJ. I always check cases, and measure before reloading. I always also follow reloading guides with no variation. I am not tempted to load hot. Thanks. Your case capacity idea is intriguing. No issue with bolt not closing, sometimes they don't, but you can never pull the trigger and get it to go bang. Varied brass lot. Mostly Winchester.

 

[writerman]

Hate to break it to you but it wasn’t out of battery when it popped

What is your thought on what happened?

 

[writerman]

The (partial?) ring at the rim of the neck is suspicious. A long (untrimmed) case could have jammed in the chamber thus raising the pressure by not allowing the bullet to release properly?
I had a similar failure in my 6mm Grendel where the case separated at a similar distance from the head. The pressure bleed through the firing pin hole and wrecked the carrier. Amazingly, the bolt survived with the exception of the loss of the pressure rings. Upon subsequent examination I found a small strip of plastic (bag?) in the chamber when a loaded round would not seat while I was diagnosing the problem. Was that enough to cause a pressure excursion? I don't know.

I was thinking some debris from firing got into the chamber. I always trim and measure my cases. I have had primer holes right through the primer on 6.5 Creedmoor, primers popped, and nothing like this ever happened before.

 

[writerman]

I keep thinking through possibilities but they all circle back to the reloading bench.
Please give us more info on reloading tools (press, powder measure, etc) and on the components used (powder, primer, brass, bullet & weight). Example: a shooter blew up his 6.5 Creedmoor bolt gun. It was not repairable but the builder kindly told him he would build another free of charge. Two months later he blew the magazine and ejector out of that one. While I wasn't there when the first problem arose I was for this instance. He was adamant he didn't do anything wrong at the reloading bench but I did get him to promise to pull bullets on a couple. He called me and said he was using an Autothrow and had forgotten to clear the powder measure's metering chamber of H4895 before going to what he thought was 41 grains of H4350 for the Creedmoor.

Just to let you know, I always completely clear my powder before going on to any other load. Always measure and trim if necessary. All loaded the same amount, 23.5 grains of H335. OAL 2.245. I am fairly convinced it fired out of battery, brass deformation indicates that. Cracked the upper, lower, blew the magazine apart, cracked the barrel extention in half. Really glad I was holding the front grip and not the magazine for that one. I will never wrap my hand around the magazine again.

 

[writerman]

More pictures please
View attachment 1542157
Brass flowed deep into ejector hole?
Flat primer still below flush with crater?
Extractor pulled the case rim off and case blew out?
Bolt is trash, right? Broken lugs?
Too much gas and over pressure?
Caliber, headstamp, and gas port size?
Missed the .223 in the first post.
Looks like some of the case damage was from pulling the blown case out.

Case was jammed in the chamber, had a heck of a time getting it out. Cracked the extention in two, ripped up the bolt, bent the extractor, and interestingly blew OUT the extractor pin so I did not find it, blew out the magazine, cracked the upper and the lower. Safe to say, rifle is now in the trash. Only thing saveable was the trigger and stock. PAC headstamp. Was not a slam fire. Pulled the trigger and bam! No barrel obstruction. No broken lugs, just cracked in half bolt.

 

[writerman]

Was this a Federal case with a thin web and not reloadable?
View attachment 1542173

Extreme high pressure. Look at the amount of brass flow into the ejector hole.

Hal

I know, but from what possibly?

 

[writerman]

I had a problem like this once but was not as catastrophic. Only my upper and bolt carrier were blown. The bob sled single shot sled and the lower were just fine, so mine was a lot less pressure than this.

Turned out that it was an obstruction in the case. I had been reloading gas checked cast bulled with the brass. During my testing of different loads I ended up disassembling a batch that didn't perform well. During that process I did not catch that one of the gas checks was left behind when the bullet was pulled. Then when resizing, the check was pushed and pinned to the bottom of the inside of the case.

Went to shoot the next batch of test loads and BOOM. Looked very similar to the OPs pic, except that mine was much less pressure thankfully since I was testing lower velocity cast loads. If it was a full power jacketed load, man it would a been bad

That's the long way of saying, your case had an internal obstruction.

Stainless steel pin? Tip of your depriming rod? Flash hole obstruction? Old gas check if you have ever reloaded cast bullets. Something was in that case obstructing and that gas had no where to go but out the back of the case. Glad the shooter was not injured.

Thanks. I'm glad I wasn't injured either. So you're saying, a stainless steel cleaning pin could have been in the round accidentally? That would have caused all of this?

 

[writerman]

A really definitive statement.

Exactly. Why I need an answer somehow.

 

[writerman]

Powder trickler cleared of Bullseye before you started reloading these?

I always clear my powder from the loader before progressing.

 

[writerman]

I in no way mean to offend you, but could your eyes or memory be starting to slip while you're at the reloading bench?

Considering that the rest of the rounds were fine, I don't think that was the problem. I am careful. Always trim, always measure. It's very hard to overload a .223.