Out Of Battery Detonation AR

[Herzo]

the cone on the face of the barrel was cut too deep and a piece of brass that the web was too low created a unsupported casehead and it blew the brass out. This stuff happens all the time. But usually it just leaves a belt around the brass. Everyone always goes right to you loaded the cartridge too hot.

I have been in way too many conversations with people when this happens. Go back and read everything I have posted.

Im done

That does not explain the extreme pressure as evidenced by the extrusion of the brass into the ejector hole.

 

[Rocketvapor]

Thanks for the second case picture.
Here's my take on this.

Extension cracked from bolt failure, likely while locked in.
OOB would have done all the damage you had, but bolt would have been blown back. HARD.
Cracked extension indicates (to me) a locked in bolt.
Firing on trigger pull also indicates a locked in bolt.
A cracked bolt head from previous firing could have created a very weak lockup. Bolts do fail.
I think we can eliminate OOB.

Now, on to excessive pressure.
Ejector hole was filled by the brass. That's a lot of pressure. I'm sure that has happened before, I've just never seen that much.
Sometimes I get a few thousandths and have to face off the base a little. To blow that much brass from the base (not thin) into the ejector hole is pressure. Someone give me another reason.

Gas pressure would be much higher with a high pressure discharge, pulling on the case rim with the case locked into the chamber, pulling off the rim, weakened the case base allowing the blowout. I shoot the famous 22 Nosler, and excessive gas causes pulled rims, and smears.

The blowout probably took out the bolt head in the area of the extractor that has no rim support. That is the most likely spot to blow a bolt. That, or adjacent broken lug. Extractor pin broke when extractor blew out. Were all lugs intact with the cracked bolt?

Brass is also suspect. Thin spot in the unsupported area or a thin web. The old Federal thin web issue blew out webs and damaged rifles when reloaded. 0.180" was the web thickness deemed reloadable.

I give you a pass on the actual reloading. I don't know how much of that powder you can cram into a .223 case anyway. How close to compressed is your load?

Bullet push back, from a chamber tightened by carbon, could be a cause of excessive pressure.

Pin in flash hole would have blown primer, reduced flash into powder column. Probably not the case.

If you plan on this NOT happening in the future, DON'T toss out any parts or components. Something may come from a future exam. Impossible with stuff sent to the landfill
Glad all fingers are still intact and functioning.
Best to you in the furure.

 

[Kevin1990]

Have you read what I said? You had a bad piece of brass with a defective barrel. Thats it. Thats what happened. Throw away all of that brass. For one I have never heard of it.So that right there is suspect.

Wipe up your tears and buy new stuff.

People like you need to stay off forums like this. Guy is asking a question. As if your opinion is somehow more important than the other 6 pages full. Get over yourself.

 

[L1986]

No one has mentioned it that I’ve seen yet but mixing headstamps is a bad idea. I’ve never heard of the brand you had the blowout with but it is possible that it has significantly less case capacity as opposed to the Winchester brass that the other rounds are which can cause extreme over pressure

 

[dellet]

Overpressure. Yes. But how? Why? I would really like this to not happen again. LOL! Destroyed the whole rifle, cracked the barrel extention in half, split the bolt, cracked upper and lower, not to mention it was not fun. Loaded PAC with 23.5 grains of H3335 OAL 2.245, 55 grain .223 all the same batch. It was the ONLY PAC in the batch, however, all the rest were Winchester. I was thinking, maybe the walls of the PAC are different, less case capacity? That might cause overpressure?

You had one piece of odd brass, and that same round gave you results something like the above photo.

Generally that would be considered a clue.

If the headstamp was truly PAC, which does not appear to be correct because PAC produced polymer cases and went out of business. It would explain a lot. More likely PMC, and they tend to vary a lot in case thickness. They have multiple headstamps that seem to make a difference over the years.

A quick look at load data and 23.5 grains of H335 is either over Maximum or a starting load. So seating depth and case capacity seems critical with that combination.

It you are using a crimp die, or die with that capability, an odd piece of brass will likely have a different crimp. Could be the only one with a crimp and be excessive, or no crimp at all. A heavy crimp will surely increase pressure and no crimp could allow the bullet to slide forward and jam. Again increasing pressure.

Sounds more and more like an error on the loading bench.

 

[JerkyFreak]

No one has mentioned it that I’ve seen yet but mixing headstamps is a bad idea. I’ve never heard of the brand you had the blowout with but it is possible that it has significantly less case capacity as opposed to the Winchester brass that the other rounds are which can cause extreme over pressure

Not an expert here, but to reduce the volume of the case by that much, wouldn't the powder overflow first? If not overflow, but appear much fuller than normal. That should be easy to see if using a single stage press.

 

[Rocketvapor]

"It was the ONLY PAC in the batch, however, all the rest were Winchester."
I missed that line.
I wonder what the weight difference is between the PMC and Win brass?

 

[brokeasajoke]

I am listening an learning and this question will probably reveal my ignorance and lack of knowledge, but is it possible somehow the case did not grab the chamber and this was 100% bolt thrust and the failure/fatigue in the metal was there before this round fired?

 

[shoot4fun]

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.

I don't know you at all and certainly don't know what safeguards you have for powder handling and I certainly don't want to do anything other than help pinpoint the reason for the failure.
I won't adamantly say the AR15 platform cannot fire OOB because it is a mechanical device and we all know the possibility for eventual mechanical failure is very near 100% and someone could come along and prove it can happen. Let me ask this; have you had any ammo (factory or reload) that went click instead of bang because the bolt didn't quite into battery? That is an OOB condition I have experienced and (after years of range time witnessing thousands of AR shooters) there has never been a single issue of FOOB.
I think you should be honest in this instance, understand that this calamity most likely started at the reloading bench and intensely pour over every single step of the process. Not just the process concerning the batch of ammo that produced this problem but the one before that. Respectfully, I would say the first step to finding the problem involves looking in the mirror and not being too proud to think the guy you see isn't capable of making a mistake. I have been reloading since 1975 and I know I have along the way. Thankfully the outcome was not catastrophic.

 

[TrapperBR549]

Just to clarify, there was a post about a gas check being stuck in a case and causing an over pressure situation, not a stainless tumbling pin. At least that I saw.
This stuff is way over my head but if 50 Winchester cases worked perfect and the first "PM?" blew up that sure seems suspect to me.

 

[whatsupdoc]

the cone on the face of the barrel was cut too deep and a piece of brass that the web was too low created a unsupported casehead and it blew the brass out. This stuff happens all the time. But usually it just leaves a belt around the brass. Everyone always goes right to you loaded the cartridge too hot.

I have been in way too many conversations with people when this happens. Go back and read everything I have posted.

Im done

No, wrong. That has nothing to do with this. The brass extruded into the ejector hole
from OVER PRESSURE not case failure due unsupported case head.

 

[ebb]

International Ammunition Assocation doesn't list a PAC. A quick search shows that there has been confusion with PMC being mistaken with PAC, check with lope or magnifying glass to be sure. I have loaded PMC a lot of times and had no issues, I do not believe it will last over the long haul like Lapua or good brass but it works. Made in Korea. Could it be possible that ONE of the cases slipped through the OAL trimming process and was too long? I had several when I made 260 rem brass out of 308 win that were too long, It caused so much pressure that the headstamp engraving was gone from the case, primer was in the magwell, very hard bolt open. A long case allows the neck to get pinched down on the bullet due to the narrowing of the chamber at that point in the barrel and causes a way overpressure condition. Didn't blow up my gun but came way closer than I would have liked.

 

[jelenko]

No, wrong. That has nothing to do with this. The brass extruded into the ejector hole
from OVER PRESSURE not case failure due unsupported case head.

OP - As whatsupdoc and others have said, the brass extruded into the ejector hole is proof that there was extreme over pressure when the round went off and that it was not OOB.

The only remaining question is how did it happen? Followed by how to avoid it in the future.

 

[whatsupdoc]

1) 23.5 gr of H335 behind a 55gr bullet is a safe load, I have loaded and fired THOUSANDS of Hornady 55gr FMJ's behind 24gr H335 in mixed range pickup brass.

2)The breach was locked, over pressure caused the case head to fail destroying the
bolt carrier. (The bolt carrier getting destroyed when a case fails in an AR is common)

3)The cause of the over pressure was most likely a mistake made during the reloading process or a mistake during shooting.


Possibilities

Over charge
Wrong weight bullet mixed in batch
Powder measure not emptied from previous use, wrong powder
Foreign material left in case reducing capacity

Is it possible you dropped the bolt carrier loading a round in the chamber then ejected the round without looking for the round you ejected.

Because then it is possible the bullet was left in the chamber and a new round was
loaded behind it and boom.

 

[dellet]

International Ammunition Assocation doesn't list a PAC. A quick search shows that there has been confusion with PMC being mistaken with PAC, check with lope or magnifying glass to be sure. I have loaded PMC a lot of times and had no issues, I do not believe it will last over the long haul like Lapua or good brass but it works. Made in Korea. Could it be possible that ONE of the cases slipped through the OAL trimming process and was too long? I had several when I made 260 rem brass out of 308 win that were too long, It caused so much pressure that the headstamp engraving was gone from the case, primer was in the magwell, very hard bolt open. A long case allows the neck to get pinched down on the bullet due to the narrowing of the chamber at that point in the barrel and causes a way overpressure condition. Didn't blow up my gun but came way closer than I would have liked.

just in case you’re interested

PAC / PCA headstamped Plastic cased cartridges

I have three cartrigdes with plastic cases. Two .223 Remington and one .38 Special. The .38 Special is all grey plastic, with brass primer. The headstamp is: “P A C 38 SPL” The first .223 is made of grey plastic, with a brass base, coming about 10mm (0.4") up the case. The primer is...

forum.cartridgecollectors.org

PCA-SPECTRUM AMMUNITION FROM NATEC PLASTIC FANTASTIC - Small Arms Review

Text & Photos by Jeff W. Zimba

smallarmsreview.com

It would be hard to confuse these PCA stamped cases.

 

[Dimner]

People like you need to stay off forums like this. Guy is asking a question. As if your opinion is somehow more important than the other 6 pages full. Get over yourself.

Glad someone said it.

 

[Rocketvapor]

Another picture request
Showing the case about 90 degrees around from the blowout.


I now have won the sheety picture award

 

[jsn]

Only several things I haven't seen asked yet:

1) Did you weigh each individual powder charge?
2) Did you perform any type of examination of the powder charged brass before seating the bullet (ie: take a flashlight an look down into each casing while in a tray)?
3) Did you weigh the empty cases at any point? If not, can you weigh what's left of the PAC case and several of the Winchesters and let us know what they weigh?

 

[Coyotefurharvester]

I run both PMC( with my readers the M looks like an A in poor light) and Win, LC thru my 20p. PMC Brass weighs low 90's (91-93 gr. ish) very similar to Win. I have not noticed any brass issues using same charge/bullet in both brands.

 

[Rocketvapor]

I did some searching and PMC, light like Winchester, but no problems out there.