Face full of flying gun parts is what I got from my RAW

[G-forceJunkie]

Not to mention, the firing pin cannot hit the primer when out out battery, and that case has a nicely centered firing pin hit. You just got a crazy high pressure round, or a really defective case from the factory that loaded it.

Originally Posted by ar15barrels

That's NOT an out-of-battery pressure event.
That case was FULLY in battery when the case blew up.

I can tell because of how the flow of the brass went into the ejector hole and extractor cut.
If the gun was out-of-battery, the case would not be seated in the boltface and the case would have yielded forward of the case head where the case wall gets real thin.

[ar15barrels]

Originally Posted by five.five-six

His thinking is that the firing pin became stuck and acted like an open bolt; KB; sent BCG into the receiver extension and the spring sent it back home where it was stuck hard when I got to it.

That's not possible.
The firing pin can NOT protrude out of the boltface on an AR until the carrier is against the barrel extension.
Also, the case can NOT be against the boltface until the cartridge is seated in the chamber and the carrier depresses the ejector enough for the bolt to be able to lock into the barrel extension.
Those are safety features to make sure the gun can't fire partially locked.

If you didn't pull the trigger yourself, you had some sort of fire control related problem that caused the hammer to fall when you did not intend.

In either case, that has NOTHING to do with the high pressure event you experienced.
The high pressure event was either from a bore obstruction or from a faulty round of ammo.
No way to know without knowing more about the round that was in the gun before this happened.

[ar15barrels]

Originally Posted by five.five-six

Offhand measurement says it was about 72 thousands out of battery at the time of KB

huh?
What are you even measuring?
The location of the chamfer at the mouth of the chamber?
Do you even understand how the AR bolt, barrel extension, barrel and carrier interact?

[five.five-six]

Originally Posted by ar15barrels

huh?
What are you even measuring?

the distance from the start of the bulge in the case to the lug face.

The lugs land on the face of the chamber behind the lugs on the barrel adapter so that bulge is how far out of battery the case what’s at the time of the overpressure event.

[ar15barrels]

Originally Posted by five.five-six

the distance from the start of the bulge in the case to the lug face.

The lugs land on the face of the chamber behind the lugs on the barrel adapter so that bulge is how far out of battery the case what’s at the time of the overpressure event.

Are you making an assumption that the front of the lugs are right at the back of the barrel?

They are not.
0.010" to 0.020" lug clearance is common.

Then there is the chamfer at the chamber mouth.
That chamfer is often around 1/16" deep.
So that gets you about 0.072" right there, give or take the variances in lug clearance and chamber mouth chamfer which could be 0.010" to 0.020" in either direction based on what the manufacturer chose to do.

The bolt HAS to be fully locked into the barrel extension BEFORE the firing pin can poke through the boltface.
There's NO WAY your cartridge fired out-of-battery.
The case was against the boltface as evidenced by the ejector and extractor flow.
Before the case will BE against the boltface, the case has to stop in the chamber so that the carrier can depress the spring loaded ejector.
Before the primer can be hit by the firing pin, the firing pin has to be sticking through the boltface.
That can't happen until the bolt is locked into the barrel extension as the upper receiver won't LET the bolt rotate in the carrier UNTIL the bolt lugs are inside the barrel extension and the firing pin can't stick through the boltface UNTIL the bolt rotates into lockup in the barrel extension.

I don't think you fully understand how the barrel, extension, bolt and cartridge all interact.
Go read this again: www.ar15barrels.com/prod/operation.shtml

[five.five-six]

Originally Posted by Ar15barrels

Are you making an assumption that the front of the lugs are right at the back of the barrel?

They are not.
0.010" to 0.020" lug clearance is common.

Then there is the chamfer at the chamber mouth.
That chamfer is often around 1/16" deep.
So that gets you about 0.072" right there, give or take the variances in lug clearance and chamber mouth chamfer which could be 0.010" to 0.020" in either direction based on what the manufacturer chose to do.

The bolt HAS to be fully locked into the barrel extension BEFORE the firing pin can poke through the boltface.
There's NO WAY your cartridge fired out-of-battery.
The case was against the boltface as evidenced by the ejector and extractor flow.
Before the case will BE against the boltface, the case has to stop in the chamber so that the carrier can depress the spring loaded ejector.
Before the primer can be hit by the firing pin, the firing pin has to be sticking through the boltface.
That can't happen until the bolt is locked into the barrel extension as the upper receiver won't LET the bolt rotate in the carrier UNTIL the bolt lugs are inside the barrel extension and the firing pin can't stick through the boltface UNTIL the bolt rotates into lockup in the barrel extension.

I don't think you fully understand how the barrel, extension, bolt and cartridge all interact.
Go read this again: www.ar15barrels.com/prod/operation.shtml

I do understand all that much at least.

While it’s obvious that the face of the bolt lugs don’t contract the barrel with much force by the simple fact that if you find much wear there it’s indicative of a problem and I didn’t know the specification or tolerance was 0.010” it’s the best measurement available to me. I did see the chamber chamfer and did account for it.

I’m well aware that the firing pin “can’t” strike the primer without being in battery but that begs the question: How did I get a strong primer strike?

Was it just an overpressure? from what? Bullet setback? “Double charge”? Barrel obstruction?

This is what I want to know.

[ar15barrels]

Originally Posted by five.five-six

Was it just an overpressure?

YES.

Originally Posted by five.five-six

from what?

This:

Originally Posted by five.five-six

“Double Over charge”?

Your pressure event was pretty mild.
Bullet setback won't do much in a rifle case.

Bore obstructions cause MUCH higher pressure.
We normally see the bolt carrier peel open and take out the upper reciever.
The fact that your bolt and carrier survived without significant damage tells me that you were not much over 80-90K psi.
The extractor is a separate part from the bolt and is always the first thing to go and your only got bent.
The front part usually separates from the rear at the pin.

This leaves us with ammo as the cause.
You had an overcharged case.

[subscriber]

Either there was another bullet stuck in the barrel just ahead of the chamber, or the case head was soft. As case heads are deliberately left in the work hardened state, from the last few steps in deep drawing the case during manufacturing, a soft head could only result from deliberate annealing that included the case head (or the the whole case). This is not something done at any factory you would normally care to buy ammo from.

Case volume is not enough to take a double charge; so another possibility would be a little too much, or the wrong type of propellant was used. As there was a failure to eject directly before this kaboom, my vote is for a defective load that left its bullet (or just a partial jacket) just deep enough into the barrel so as not to prevent loading the next round.

What are the striations on the case neck? They almost look like rifling land impressions, although that makes no sense.

Anther possibility is that a round of .300 BLK subsonic (not full power load) somehow got into the mix:

[subscriber]

Hopefully it was not something like this that lead to the kaboom: https://youtu.be/oEV15uVnhG4?t=74

[Spyder]

Was it that Federal ammo in the ...was it white and blue box with a star on it Independence or something like that? that had a bunch of really hot ammo a couple years ago? Several anecdotal stories of people having problems with that ammo a couple years back.

[Spyder]

Brief looking over coffee, I can't find the threads with reference to it so I may be wrong about the brand, but I'm almost sure that a couple of people came up with independent complaints about that ammo over a short period of time several years back. I could be wrong.

[FromTheGrave]

Originally Posted by Spyder

Brief looking over coffee, I can't find the threads with reference to it so I may be wrong about the brand, but I'm almost sure that a couple of people came up with independent complaints about that ammo over a short period of time several years back. I could be wrong.

I believe you're talking about Hornady Frontier ammo.

[RAMCLAP]

Originally Posted by The War Wagon

RRA is JUST as good as any $2,000 rifle!

Beat me to it.

[alpha_romeo_XV]

The partially visible letter on the head stamp in the extractor area looks like an "F" to me for FC Federal Cartridge. I'd pull down one of the remaining rounds from that box and weigh the powder charge.



I was doing some chrono work last week with a new 16" barrel and some hand-loads but I included a few factory Federal 55g for reference. I was getting 3170 fps average with the Federal ammo which is pretty darn hot in a 16" and more than I ever reload at. I had one of 5 shots of Federal read 3255 and I could feel difference in recoil. I can get "calibrated" pretty quick to recoil and know right away when i feel a soft or hard shot.

[SVT-40]

Massive case failure. It's a ammo issue not a gun issue. The case head failed in a catastrophic manner causing all the gas to vent out through the magazines if the bolt wasn't locked at the time of the failure the force of the event would have blown the primer out of the case. The expanded portion of the rear of the cartridge case was due to the massive gas pressure escaping from the case failure.

[2shotjoe]

You still have the lugs on the barrel?

Sent from my SM-N975U using Tapatalk

[sammy]

Since we are all experts here I will give my 2 cents. AR15 barrels is 100% correct. Look at that primer. If that case was out of battery there is absolutely no way you would have a primer that flat and the ejector mark so deep. An out of battery primer would look almost new due to the case rupturing before even 50% of the capable case pressure could be achieved.

Have you taken a close look at your barrel? I would bet you had an obstruction and could have some kind of scarring inside the bore.

[five.five-six]

The gun still shoots fine with a different BCG.

[five.five-six]

Originally Posted by SVT-40

Massive case failure. It's a ammo issue not a gun issue. The case head failed in a catastrophic manner causing all the gas to vent out through the magazines if the bolt wasn't locked at the time of the failure the force of the event would have blown the primer out of the case. The expanded portion of the rear of the cartridge case was due to the massive gas pressure escaping from the case failure.

I think you are probably correct.

I also like how you come right out and clearly state your opinion instead of dancing around for a day or two like a menstruating woman trying to start an argument.

[sammy]

Originally Posted by five.five-six

The gun still shoots fine with a different BCG.

Glad you are OK. Buy a lottery ticket.

[jtv3062]

Nvm

[Spyder]

Originally Posted by five.five-six

I think you are probably correct.

I also like how you come right out and clearly state your opinion instead of dancing around for a day or two like a menstruating woman trying to start an argument.

You... you do realize that the correct answer was given very succinctly and precisely to you pretty early on in this discussion, and you immediately answered by going on about how your gunsmith told you the same thing, but you still thought it was OOB?

Originally Posted by ar15barrels

That's NOT an out-of-battery pressure event.
That case was FULLY in battery when the case blew up.

I can tell because of how the flow of the brass went into the ejector hole and extractor cut.
If the gun was out-of-battery, the case would not be seated in the boltface and the case would have yielded forward of the case head where the case wall gets real thin.

^here...

Originally Posted by five.five-six

That’s right in line with what my armorer said. And even matched up the blown out parts of the brass with the extractor and ejector locations on the bolt. The question is: how did it happen because that’s not a light primer strike like you see in slamfires, the primer strike is what made me think there was another round behind it? The question is: how did it get that heavy primer strike out of battery?

followed by "nah, my armorer said that too, but how did it happen out of battery?"

[five.five-six]

Originally Posted by Spyder

You... you do realize that the correct answer was given very succinctly and precisely to you pretty early on in this discussion, and you immediately answered by going on about how your gunsmith told you the same thing, but you still thought it was OOB?




^here...



followed by "nah, my armorer said that too, but how did it happen out of battery?"

You seem awfully upset. Perhaps you should take a breather. From the very beginning, I said what I thought had happened, what I had been told by trained expert and asked questions.

You must be angry about something else, it’s not good to hang on to anger.

[Spyder]

No way. I hear high blood pressure is good for you! Like having a high volume water pump on an old hot rod!

[AGGRO]

Originally Posted by deckhandmike

As a lefty that scares the crap out of me. I fear the day a gun explodes across my face.

I'm a lefty and had an ar fire out of battery. Somehow the bolt came apart and it did not lock up fully. A lot of stuff came out the port but I was lucky.

[five.five-six]

Lesson learned: Make sure you tell the people you love that you love them every chance you get.


I’m going to replace the entire BCG and pull down all the 223 I have because I’m not 100% sure it wan’t one of my reloads. I’d been shooting out of a can of mixed factory ammo that I was trying to run through all day.

[ar15barrels]

Originally Posted by ar15barrels

That's NOT an out-of-battery pressure event.
That case was FULLY in battery when the case blew up.

I can tell because of how the flow of the brass went into the ejector hole and extractor cut.
If the gun was out-of-battery, the case would not be seated in the boltface and the case would have yielded forward of the case head where the case wall gets real thin.

Originally Posted by five.five-six

That’s right in line with what my armorer said. And even matched up the blown out parts of the brass with the extractor and ejector locations on the bolt. The question is: how did it happen because that’s not a light primer strike like you see in slamfires, the primer strike is what made me think there was another round behind it?

The question is: how did it get that heavy primer strike out of battery?

Do you not see the problem with your logic yet?

Originally Posted by five.five-six

I also like how you come right out and clearly state your opinion instead of dancing around for a day or two like a menstruating woman trying to start an argument.

WTF?
Are you talking about me after you completely ignore everything I have said and KEEP thinking it's an out-of-battery problem when it's so obviously NOT?

[five.five-six]

Obviously I had not figured it out yet, that’s why I asked the question. I’m still not 100% sure because, the vast majority of my .223 loading has been with varget and I don’t even know if it’s possible to cram enough varget in a case to cause a KB.

But really, I am at a loss as to why you might think I was talking about you, you have been nothing but helpful and concise throughout this thread. I don’t remember exactly who that was about, it was late I think I was thinking of someone on a different forum where we were having a similar discussion, but I don’t remember which forum, perhaps the FAL/AK files? Sometimes I just post funny stuff like that just to see who pleads guilty LOL


I still want to know how it happened. I’m not 100% absolutely sure that it wasn’t one of my reloads but I had only brought 100 of mine and I had just loaded all those into a 100 round drum and bump fired it a few minutes earlier.

The reloads I brought were 55 grain FMJ spritzer over 24.9 H355 Lymans 47th puts max load at 26.5, Hogdon’s website says 25.3 but still I weigh my first 5 char 5 charges on my 550 and ever 10th or so after that.

I’m about 99.999% sure it was one of these because I remember thinking: “there’s no way you are going to hit that 1000 yard gong with this random ammo, but some times it’s just fun to waste ammo”.


Here is the rest of that random factory ammo I have. I’m going to pull all of it down ... I don’t even know if I’ll save the primers. Heck, maybe I’ll just dispose of it. I’ve decided to just buy new matching brass. I don’t ever want this to happen again.

[ar15barrels]

Originally Posted by five.five-six

I still want to know how it happened.

I’m not 100% absolutely sure that it wasn’t one of my reloads.

The reloads I brought were 55 grain FMJ spritzer over 24.9 H355 Lymans 47th puts max load at 26.5, Hogdon’s website says 25.3 but still I weigh my first 5 char 5 charges on my 550 and ever 10th or so after that.

Nobody can tell you for sure why it happened.
We can only rule out possibilities.

I can tell you from my experience, that you did NOT have an extra bullet in the bore from a squib round because if you did, your barrel extension, barrel, bolt, carrier and upper receiver would no longer be usable.

I can tell you from my experience that there are more random blowups with FC heaqdstamped factory ammo than from the other big manufacturers like Remington, Winchester or Hornady.

I can tell for certain from your pictures that you blew up an FC case.
I recognize the stamping style/font/depth without even seeing the C from FC.

I can't tell you who loaded that FC case.

Because you are uncertain of the source of the problem ammo, the real answer will never be known.

[five.five-six]

Well, I think I have decided to dispose of all that ammo, I might pull it all down and sell it as primed brass if that’s even legal in this state.

I’ll buy 1-2K matching brass and only load my own. Any recommendations?

[five.five-six]

So this is pretty interesting, I’m going through the brass from that day and about 1/2 of it has these strange gouges in the head stamp. They don’t show up well in the photo but some of them are pretty deep. I did bring 2 ARs that day and I reviewed the brass from the bull barrel AR from a few weeks earlier when I was cronographing loads and none of those have anything like this on them







These are from the AR that didn’t KB, from a few weeks earlier.




Anyways, I’m just going to buy a lot of virgin brass and start from scratch. I just can’t get the standard devs I’m looking for with mixed headstamp without measuring water displacement on every one.

[smoothy8500]

Some pretty serious ejector swipes and "imprints" from excessive pressure.

[ar15barrels]

Originally Posted by sfarchitect

Seventy two thousandths out of battery, and that result. . . . wow!

It was NOT out of battery event.
Cartridge cases fired out of battery do not extrude case heads into ejector and extractor cuts because the cartridge case head will NOT be against the boltface of an AR type action during an out-of-battery event.

[walmart_ar15]

The previous round FTE. Is it possible part of the previous case got lodged at the throat and when the 2nd round loaded, it jam it and caused the Over Pressure.

Over pressure clear the barrel, but gas also came out the weak side of the bolt, the extractor (with weak Fed case)

An out of battery discharge would have done much much worst damage than shown. Ask how I know. :O

[CheapBloke]

I think I found a similar issue as yours on another forum which dates couple years back.

https://forums.gunboards.com/showthr...topics/1062149

Sent from my SM-N960U using Tapatalk

[NorcalGSG]

Originally Posted by tnlrat37

Had a KB like that happen to me in the Marines in Somalia in a firefight. It was at night and when I fired it sounded like a shotgun. Had powder burns on my face, ejector and dust cover blew off. Mag plate blew off, rounds dumped on the ground. Upper and lower receiver were cracked.

A little disheartening to have rounds coming downrange and all you have is a paperweight. So I made the most of it, I had a prototype ACOG at the time and used my nvg’s up to the ACOG to help the Machine gunners next to me get on target because they couldn’t see anything. Just walked there tracers on target.

Be sure to have someone qualified check for small cracks everywhere, some of mine were very hard to see. It was beyond repair and trashed after. Good luck.

Glad you made it home from that!!! Lots of poor young men didn't make it back from Vietnam when their m-16's failed also. Talk about pucker factor right there!

[five.five-six]

The upper has been sent back to RRA for them to give it the once over and replace and headspace the BCG


The big brown truck of happiness delivered this today

If I have another ammo problem, it will be on me.

2k unfired NORMA .223

[USMCM16A2]

5.56,


Glad you are ok bud. I agree with Randall, it looks like a over pressure round. Good luck with getting everything back to normal. A2

[GizmoSD]

Are you loading to 5.56 pressures for use in a .223 chamber? If I’m not mistaken, RRA chambers in .223. What is your other AR chambered in?

[Two Shots]

AR's can be replaced just glad your OK.