I had an out of battery detonation, brought the destroyed .223 AR to one of the best gunsmiths in town, and he just shook his head and said he thought it might have been 'something about the round the gun didn't like.' I reloaded 100 rounds, same everything, no variation in that box at all. 50 went through perfectly, no squibb either, and then number 51 boom! Here's a pic of the round. The dent marks are from trying to get it out of the barrel extention. The magazine was blown open, the upper cracked, the bolt end split, the lower slightly bent/may be salvageable, the barrel extention cracked, the bolt catch split, not much was not affected. Has anyone had this happen before? First time in fifty years of shooting, most times every week. I need to know what happened. Maybe someone has had this experience before.
Out Of Battery Detonation AR
- Thread starter writerman
- Start date
What brass is that? The web looks quite thin.
Rocketvapor
Gold $$ Contributor
That's about the most severe ejector mark I've ever seen.
More pictures of the case would be interesting.
Caliber and headstamp?
More pictures of the case would be interesting.
Caliber and headstamp?
About all anyone can do is guess. A high primer can do that. A trigger without enough sear engagement so the hammer follows the bolt can do that. A stuck firing pin could do that.
jepp2
Gold $$ Contributor
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.
Rocketvapor
Gold $$ Contributor
#51 blew, 49 suspect rounds left.
The (partial?) ring at the rim of the neck is suspicious. A long (untrimmed) case could have jammed in the chamber thus raising the pressure by not allowing the bullet to release properly?
I had a similar failure in my 6mm Grendel where the case separated at a similar distance from the head. The pressure bleed through the firing pin hole and wrecked the carrier. Amazingly, the bolt survived with the exception of the loss of the pressure rings. Upon subsequent examination I found a small strip of plastic (bag?) in the chamber when a loaded round would not seat while I was diagnosing the problem. Was that enough to cause a pressure excursion? I don't know.
I had a similar failure in my 6mm Grendel where the case separated at a similar distance from the head. The pressure bleed through the firing pin hole and wrecked the carrier. Amazingly, the bolt survived with the exception of the loss of the pressure rings. Upon subsequent examination I found a small strip of plastic (bag?) in the chamber when a loaded round would not seat while I was diagnosing the problem. Was that enough to cause a pressure excursion? I don't know.
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shoot4fun
Gold $$ Contributor
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.
jelenko
Gold $$ Contributor
And, the primer looks to be about flat as it can be.
Is that really the ejector mark in the far side of the base? If it is, it looks deep.
Rocketvapor
Gold $$ Contributor
More pictures please 
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.
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?
Missed the .223 in the first post.
Looks like some of the case damage was from pulling the blown case out.
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Coyotefurharvester
Silver $$ Contributor
If able to answer jepp2 questions , also was this full auto fire? Suppressor?
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