• This Forum is for adults 18 years of age or over. By continuing to use this Forum you are confirming that you are 18 or older. No content shall be viewed by any person under 18 in California.

Out Of Battery Detonation AR

tommeboy said:
The AR15 has what is called a coned breech face. It is a beveled face to help the round to feed. When a manufacturer cuts this cone too deep bad things can happen. But usually it takes other things that are out of spec to make a catastrophic instance to occur.

You had multiple things go on that caused this. One was the improper cut barrel. Two was a case head the web was too shallow so with the casehead now being unsupported by the chamber. And a possible over loaded cartridge the case blew out from not being supported.
Click to expand...
I don't think you can state that as fact without more info. Logic tells me that if that were true, ALL of the rounds fired would exhibit similar failures. Thin at the web or not, if the case is not supported adequately at the extension, it will most likely fail. The OP, while reticent with his follow-up comments, made no mention that this was a new barrel. If it wasn't, why didn't this occur earlier? I will say that I don't believe this to be the problem.
 
In addition to pulling the remaining rounds I would look at the 50 that fired for blanked primers that could have locked up firing pin.
Now, that WOULD cause an OOB.

I'm sorry if any of my comments seem to be blaming this on reloaded ammo and not faults with the AR platform, just the way it is.
 
M-61 said:
View attachment 1542300
This is only to reply to "impossible" if out of battery is implied. Here is a 5.56 fired out of battery and result was a magazine blown out. No other damage. But I now have a perfect 'BELTED" 5.56 No clue to what the OP did.
Click to expand...
I thought you had me on ignore.

How can a belt happen? The bolt is coming unlocked before pressure subsides.


Think of the relationship between the cam-pin, bolt, and firing pin. If it were fired out of battery, the case mouth would have expanded to the size of the chamber. You'd see an extremely short neck or a new shoulder. Usually OOB results in a rupture and/or primer blown.

The only way an AR15 can fire out of battery is that the AR15 didn't fire it, a foreign object was between the bolt head and the primer.
 
Last edited:
Looks like over pressure and hyper cycling.

Note the hole in the case is 180* from the ejector. The case likely did not blow apart, it was pulled apart by the extractor since the body was welded to the chamber wall.

The cracked barrel extension is proof of extreme over pressure.

Since pressure will take the path of least resistance, out the magazine, to build enough pressure to crack a barrel extension, the bolt would need to be locked shut sealing the chamber.

A reasonable load, fired out of battery would just blow the case.

Remember peak pressure is long before the gas travels to the carrier. Driving the the bolt face straight through the extension vs twisting it to release is what splits the extension.
 
M-61, Seen that before, just not as bad. Figured either brass was undersized from factory near the head or it was fired in a chamber that was way over cut at the .200 location. Curiosity got the better of me. Took a couple home. Resized, left just enough to hang a fingernail on when going from rim towards mouth, supporting the theory that brass was under diameter from factory. Loaded and fired a couple rounds using my normal light 55fmj loading, but fired in a R700. Shot ok. No more big bulge. Still a couple thou larger at .200 but nothing to hang a finger nail. Reloaded 'em again. No problem. So clean an repeat. First fired looked ok. Fired couple more with out looking them over. Went in and noticed several had actual separation for about 20-30 degrees around at .200. Would hate to think what a full power load would have done. So if it don't look right, put it in the recycle bucket!

Frank
 
Anyone really serious about reloading should fine tune their measurement and photographic capabilities.
Any ANOMALY needs to be investigated. Notice anything unusual STOP, collect, before moving on.
Measurements, photos, spent rounds collected, maybe even section cases.
 
drop_point said:
I thought you had me on ignore.
Click to expand...
Didn’t know I had anyone on ignore but before I go one bit further I will check this with the forum boss In case I have forgotten something. Anything is possible.
 
1. If the OP would do it, a careful cross section of that case might reveal a too thin case wall,
or signs of a case stretched case ring -very thoroughly covered in other threads.

2. The very pronounced ring just above the separation (almost looks like a pipe cutter did it)
does strongly suggest an incorrect forcing cone cut, which might have combined with a
too thin case wall; but, it would also seem that would have become evident in earlier firings.

3. Did not see any mention of the brass -was it a first reload on the OP's 1F brass, range pickup, or?

4. Powder measure: Last year, a local shooter totally disintegrated a CA MPR 6.5 Creedmoor.
He has decades of reloading experience, and has stopped discussing the event. But, I strongly
suspect the mentioned probability of a wrong powder left in the measure or trickler chamber.
If he had not had his left hand squeezing the rear bag, he absolutely would be missing fingers.

He was honest to admit to the rifle manufacturer that he was using handloads -and he said (it
seemed to him), they could not hang up fast enough. In no way am I faulting the mfg for that.
 
M-61 said:
View attachment 1542300
This is only to reply to "impossible" if out of battery is implied. Here is a 5.56 fired out of battery and result was a magazine blown out. No other damage. But I now have a perfect 'BELTED" 5.56 No clue to what the OP did.
Click to expand...
Not fired out of battery. See my previous post. It only happens when all things line up wrong on a load that goes over 45K psi. After that brass can not contain the psi unless there is support to keep it in
 
My guess is the gun was piercing primers, part of the primer got stuck in the firing pin in the bcg. When the bolt was pushing a new round forward with the pin stuck the round went off.
 
Looking at the neck, it seems a bit short. Possibly the shoulder moved forward too, due to the wear just below it. Potentially a different weight/longer bullet got mixed in, stuffed into the lands on an already hot reload, soft primer like a WSR and caused a slam fire and overpressure.

Only time I've seen anything like this was also a 223, but a R700. Older gentleman a couple benches over just firing away at a pretty good rate. Like he was determined to shoot 200 rounds and be home for lunch. Then one really big bang! Gun did what it was supposed to do, vented gas and contained it. Case head extruded into and completely filled the bolt face. Took some serious prying with pliers to get it out for him. I told him to get the bolt checked, but he looked it over said it was fine and went right back to shooting as fast the the RSO would allow. He must have shot another 75-100 rounds after that. Packed up and went home. Never even pulled his target.
 
You must log in or register to reply here.

Upgrades & Donations

This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.


Click Upgrade Membership Button ABOVE to get Gold or Silver Status.

You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.


To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.

Classified Ads

Forum statistics

Threads
165,467
Messages
2,196,419
Members
78,936
Latest member
Mitch.Holmes

Share This Page

Back
Top