My AR-15 goes KABOOM!

[AlaskanMBR]

My AR blew up!

1) What was the equipment used, and
GG&G Dominator upper on a Stag Arms lower.
2) What type of ammo was used?
HSM 55grn Pointed soft tip lot code 0847-7 SL/SK
3) What kind of damage was incurred?
-Upper receiver cracked and bowed out on both sides, dust guard and pin seriously bent
-Lower receiver bowed out on both sides
-Pieces of bolt carrier blown out the mag well (along with mag and bullets) as shrapnel
-Mag release mechanism blown out the left side as shrapnel
4) What makes you think it was the ammo and not the rifle?
Rifle had functioned fine for ~1500 rounds (new rifle) cleaned it religiously
5) Did the ammo manufacturer compensate you for the damage?
Still waiting to see what they can do for me (it happened last night) I've talked to Sandy at HSM and it sounds like there may be a lengthy process due to the fact that the rifle is not made by a large manufacturer

The gun must have slamfired, I inspected it afterwards and the hammer was still cocked. Only three things can cause slamfires, right?
1. Raised primer
2. soft primer
3. bolt so dirty that the firing pin is jammed in the forward position








What do you guys think???

[indy_Muaddib]

i can think of one more reason to not buy an AR.

glad it wasn't worse and glad your OK.

[ftierson]

Originally posted by AlaskanMBR
What do you guys think???

The upper receiver is FUBAR (not that I have to tell you that, I'm sure...)...

Given that the hammer was still cocked, my first guess would be a slamfire...

Anything that allows the floating fiting pin to hit the primer with sufficient force to fire it could be involved, including the causes that you mention, but also a broken firing pin with the tip protruding out of the firing pin hole in the bolt, a chunk of rock or anything between the bolt face and the primer as the bolt closed, overlong cartridge (insufficiently resized for the rifle's chamber leading to the cartridge not entering the chamber fully before the primer ignited the round), and several other even less likely causes...

Bummer about the gun.

I'm assuming that no one was hurt. That was lucky, especially if someone was standing on the left hand size of the shooter.

What does the chamber look like?

How did the ACOG fare?

Good luck with the ammunition manufacturer...

Forrest

[hagar]

I would bet money that Winchester small rifle primers are used in those rounds. Their claim to fame is out of battery slamfires. I had a highpower buddy that insisted on using them, warned him after he had the first one. He did not listen, and destroyed a bolt, upper and magazine with the second. He now uses Remington 7.5's.

[W.E.G.]

It is curious that you say it "must have slam-fired."

Do you not know for sure whether it slam-fired?
I assume you DO know what sequence of events constitutes a slam-fire.

Is the batch of HSM ammo in question constructed on previously-fired cases?

Was the bolt locked in battery when inspected after the kaboom?

Do you have a picture of the brass shell casing (or what may be left of it)?

What EXACTLY were you doing when this happened?


See http://www.thehighroad.org/showpost....95&postcount=8 for prior report of HSM kaboom.

[steveo539]

Seem like the case head could provide some good info if it could be located.

Steve

[steveo539]

PS bummer about the rifle. Good thing you're OK.

Steve

[FroggingDevil]

Man, I am glad you are OK.

But every time I think of buying an AR something happens......

I have seen another AR explode similar to yours. It was a brand new rifle with what I remember as good .223 ammo, not sure of the manufacturer.

You may have a problem getting either the ammo manufacturer or the rifle manufacturer to take responsibility for the destruction of your rifle.

If you ever used reloads in your rifle, don't tell the rifle manufacturer.

I agree with the others, need a picture of the brass case of the exploded round to help you more.

[gods pilot]

Did the upper come with a bolt and carrier or did you install one.

[AlaskanMBR]

I'm glad I wasn't hurt too... If my foot would have been one foot over I'd have a piece of bolt carrier in it.

The AR in question was custom built by a gunsmith in Fairbanks, everybody I've talked to had nothing but good things to say about him. He is a very nice guy and stands behind his work 100%. It was a beautiful gun. Before I bought it I'd told myself I'd never get an AR for the obvious reasons, but when I saw it I couldn't resist. Of course I took a lot of crap from my AR hater bros, but the gun shot like a dream and with the ACOG+Docter on top it. Luckily the ACOG made it through...

The first thing I wanted to do was take the gun apart and look at the brass, the HSM guy said definitely do not, as it needs to be opened up for independent analysis. It appears that the bolt was not in the fully closed and locked, and the hammer was still held back, it must be a slamfire right? As far as reloaded ammo, I know that HSM loads new and used brass at their factory, so technically it was reloaded brass but I believe it goes through the same machines that load their new brass. The only ammo I've ever put through it is UMC and HSM.

I'm not sure the ammo was at fault, and I am no AR expert. All I was doing was practicing moving and shooting at my home made target course, all by my lonesome.

I just hope if it is the ammo they make good and replace it, that gun was $1500, I could build 2 FALs for that!!!

[hagar]

Did the rifle go off when you chambered a round? Or you fired a round and the next one went off by itself. If yes, that is a slamfire. If it went off when you pulled the trigger, it's a kaboom...

[Survey Punk]

Never ever had a problem with Winchester primers.
Never.

JB

[armed1]

The hammer could have re-cocked as a result of the explosion pushing the bolt carrier back.

Either way, a slam fire wouldn't have fired out of battery. This is because the firing pin is not long enough to poke through the bolt until the bolt is cammed back into the carrier ( a feature designed into the gun to prevent this exact complication). The bolt isn't cammed back into the carrier until it goes into battery, hence, no battery = no slam fire.

An explantion may be that the cam pin was broken. This would allow the bolt to move backward into the bolt carrier before entering battery. This is the only way you could have had an out of battery slam fire. Cam pins have been known to fail. Have you recovered the cam pin? What parts have you recovered? SHow us the bolt, carrier, and any other pieces you have recovered.

[AlaskanMBR]

I haven't been able to get the bolt carrier out as it has been mushroomed by the bolt. Notice the substantial piece of bolt carrier that has been blown off. You can see that the bolt alignment is such that it was almost unlocked and ready to come back, but there are MAJOR shiny marks on the bolt teeth that were not there previously, seeming to indicate that the bolt was under huge pressure as it was turning to unlock. This leads me to believe the bolt was locked when the explosion occurred, what are your thoughts?

I honestly don't remember if I pulled the trigger and it kaboomed or if I fired a round and the next one slamfired. After it happened I was kind in shock.

What I can say for sure is that the firing pin still freely moves back and forth, and that when I tap on the cam pin it doesn't move or jiggle at all.

The good news is, looks like the lower receiver may be good after all! I will certainly have my gunsmith take a look at it to confirm tho...

Take a look at these pics and tell me what you think. Thanks for your input!

[W.E.G.]

Roger that on the "mushroomed" carrier and the state of shock.

I suspect you pulled the trigger on a bad round. But, since you can't say for sure, that uncertainty hurts your case for PROVING that it was a bad round. Although, I'd say the odds are much stronger on it being a bad-round KABOOM rather than a slam-fire out-of-battery KABOOM. Even if it were the latter, I think still be inclined to blame the ammo for the incident rather than the equipment or the operator.

Listen, bad rounds happen. Not like you dropped a 20 gauge round in a 3.5" chamber, then followed it with a 2.75" round of 12 gauge. I saw the aftermath of that stunt today. It amazes me that more shooters aren't hurt with these incidents. You do know Mr. Mauser (as in THE Mr. Mauser was missing an eye because of one of his WECSOG mishaps).

Anyhow, I think you should talk to the ammo manufacturer. Plead your case honestly. Worst thing that can happen now is they tell you to get lost. In which case you get to tell the world about what you think about their product, etc. Either way you get to dremel the mess all apart *salivate* and show us more cool stuff. I think you should be back in business with a new upper, bolt/carrier assembly, and a few small parts. Money-wise, its not like a trash truck ran over your Toyota.

[armed1]

The bolt, as it appears in the latest photo is out of battery.

It is unclear, however, if the position of the bolt as it is now is the position that it was in when the failure occurred. I am going to go look at some of my own, undamaged hardware and compare to your photos. Will reply.

[W.E.G.]

The bolt is DEFINITELY out of battery.

The question is:
--was it in that position when the KABOOM began
or
--was that the position it ended up in as a RESULT of the Kaboom.

[ammolab]

Originally posted by W.E.G.
The bolt is DEFINITELY out of battery.

The question is:
--was it in that position when the KABOOM began
or
--was that the position it ended up in as a RESULT of the Kaboom.

Bolt MUST have been somewhat locked at the moment of ignition or it would have moved to THE REAR at the speed of light! There would be nothing to hold it in its current position.

This might just be a catastrophic case head failure. Condition of case head..primer would tell a lot about this failure. If the case head is off the case while the primer is normal with NO indication of high pressure = case head failure.

I had an FN M193 5.56mm round fail (case head) in my SP1 AR15. Not quite as much damage as shown here...but almost.

[AlaskanMBR]

Well, considering the material worn off the back of the bolt teeth evidenced by the shine of freshly exposed steel (it's not very obvious from the photo) I now think that the bolt was probably in battery when the boom happened. I can say for sure there was no obviously worn material on the back of the teeth when I cleaned it last (the gun was still new enough that I cleaned after EVERY use) like what is apparent now. So the boom probably caused it.

I contacted HSM the morning after the incident, they were very helpful and responsive, asked me a bunch of questions regarding the incident and said that they need to investigate to determine their course of action. I can only assume this means that IF they find their ammo was at fault they will replace the damaged parts.

I will keep you updated, as I will be checking back with them probably more often than they'd like.

[gods pilot]

Keep us informed.

I love their .308 and would like to keep loving it.

[ammolab]

Originally posted by AlaskanMBR
Well, considering the material worn off the back of the bolt teeth evidenced by the shine of freshly exposed steel (it's not very obvious from the photo) I now think that the bolt was probably in battery when the boom happened. I can say for sure there was no obviously worn material on the back of the teeth when I cleaned it last (the gun was still new enough that I cleaned after EVERY use) like what is apparent now. So the boom probably caused it.

I contacted HSM the morning after the incident, they were very helpful and responsive, asked me a bunch of questions regarding the incident and said that they need to investigate to determine their course of action. I can only assume this means that IF they find their ammo was at fault they will replace the damaged parts.

I will keep you updated, as I will be checking back with them probably more often than they'd like.

Pressure from the barrel port must have unlocked the bolt...but by that time the pressure from the ruptured case head bent/broke your extractor, and the extractor, or the stub of the broken extractor, is what is keeping your bolt from moving to the rear. When you get it open show us photos of the catrtridge head or remains of same that you find in the bolt face.

[NoNotAgain]

Do you have access to a powder scale? If so you might want to weigh the remaining loaded ammo you possess from HSM and see how much variation between rounds you find and document it. A grain or three is not a big deal as 223 brass cases will have that much variation. You are looking for something very gross in scale.

Do you have any of the spent casings from this range session?

My near max (compressed loads, RE-15, CCI 41, Sierra 69 gr MK, LC 556 case) loaded rounds flatten the primers and depending on what powder HSM was using would be pretty difficult to overcharge.

The NRA has certified reloading instructors that you may be able to make contact with so that you can have the third party witness and document.

As far as attempting to fix the lower receiver to remove the bow from the magazine well, be very careful squeezing it back into shape as anodized 7075 aluminum cracks easily.

[Ksmith]

What a tradegy.

[ftierson]

Originally posted by NoNotAgain
The NRA has certified reloading instructors that you may be able to make contact with so that you can have the third party witness and document.

I agree that checking some of this ammo in the presence of the appropriate third party witness is a good idea...

Forrest

[RT]

Sir your lower is F ed also. they are cheap. get a new one. better safe than DEAD. sorry about your Kboom. i hope the ammo people will get you a new AR~R

[Kyrottimus]

They're located only a few hours south of me.


Next time I'm in Missoula, I can run down there and turn around a few knee-caps with a Louisville Slugger for ya for punishment!

just kidding

[armed1]

I doubt very much that an overcharge of powder was the problem. The case can only hold so much powder, and its not enough to cause that calamity.


Based on what I see here, it looks like there was a slam fire that occurred in "partial battery". In other words, the bolt pushed a round into the chamber, then as the carrier moved forward, it started to rotate the bolt into the barrel extension. However, before the bolt's lugs fully engaged by the barrel extension's lugs, the slam fire occurred. Since the lugs were only partially engaged, they got sheared off by the force of the explosion. This theory would also explain the hammer being cocked.

Do you have any of the brass from previous shots? Can you retreive the primers from these? It would be interesting to know if the hardness of the primers was up to spec for a 5.56 rifle.

This is not good. I like HSM ammo, especially their A-max BMG. I hope they didn't cut corners and use cheap primers.

[AlaskanMBR]

I do have fired and unfired rounds from the blow up session. I'll post some pics in a bit...

One thing I have noticed about the ammo in question is that it seems the cartridge is only about half full of powder. If you shake it next to your ear you can hear that it's half full. I wonder if you filled it to capacity if you'd have enough power to kaboom. I will take a few of the rounds apart and see how much the powder weighs.

I really do want to do an autopsy and get the brass out, but I'm sure the guy who does the independent investigation for HSM won't like that.

As for the lugs, they were 7/8ths to fully engaged from the look of the scraped steel, on all but one of the lugs that I can see there was metal taken from all the way across the backside. The lugs align perfectly in when in battery right??

As far as the lower receiver, I will certainly have it scrutinized by my gunsmith before any use and if it does have to be bent I'll just toss it.

[ftierson]

Originally posted by AlaskanMBR
IThe lugs align perfectly in when in battery right??

The bolt in your lower picture is unlocked. When in battery, the lugs riotate a small amount and should be behind the lug seats in the barrel extension.

You can also tell that the bolt is unlocked because the end of the bolt cam pin in the bolt is pointed directly downwards. When the bolt is locked in the barrel extension, the base of the cam pin that is visible (and it's visible only because the bottom of the bolt carrier is missing here) should be rotated slightly to the right of vertical.

And, by the way, you can hear 26.0gr of H335 shake around in a loaded cartridge, even though the case is nearly full with that kind of load. Don't assume that the case is only half full from some sound when shaking the cartridge.

If the case really is only half full and still cycles the action, the manufacturer used a powder unsuitable for the cartridge.

Forrest

[AlaskanMBR]

Curiosity got the best of me so I took the rifle to the local gun expert (not the guy who built the rifle)

He go the brass out in 1 second and we took a look at it.

here it is:







Here are the last few rounds that went thru the rifle before the boom:



And here's the bolt face:



He said it looked like an overload to him, but said there is a possibility the gun was not timed right.

The gun performed flawlessly up to the time the blowup happened, could the timing have gone out between one round and the next?

[kennaquhair]

Just a question to add to your report: What were the ambient temperature and sun conditions at the range, and how was the ammunition stored immediately prior to being loaded into the rifle to be fired?

It would have been nice if the pictures of the destroyed round were better but they are probably good enough to get out on a limb with.

An out of battery discharge might have destroyed the rifle with equal facility, but it probably wouldn't have left the cartridge looking like that. All of the damage to the cartridge seems to have been localized to the case head and the general condition of the case body indicates that it was fully chambered at the time that it was fired.

The primer looks as though it has been hammered. The edges on the primer appear to be flat and sharp. The brass in the primer has flowed back into the firing pin hole. This is one of the classic warning signs that you are dealing with higher pressures than those to which you want to subject your rifle. Your other cartridges look normal.

It looks as though much of the lettering depth on the case head has been ironed out. It also looks as though the case head has an impression of the bolt face embossed into it. That neat cut-out probably matches your extractor recess perfectly and the other missing chunk of the case head seems to be a good match to the relatively unsupported area mapping to your ejector recess. The cartridge appears to have failed under very high pressure -- sufficiently high to have caused shearing of the case head where it was unsupported by the bolt. To get that sort of pressure on the case head, the cartridge would have to have been locked into and supported by the chamber, otherwise the pressure would have simply vented through the thinner case wall.

If the condition of the barrel does not indicate that there was a blockage then it looks like an over charge or an inappropriate powder might have been used to create the load.

Just my two cents.

[firefuzz]

Originally posted by Survey Punk
Never ever had a problem with Winchester primers.
Never.

JB

Me neither. Probably loaded over 100,000 in all sizes. Never even heard of them being slam fire prone.

Rob

[ammolab]

Originally posted by kennaquhair


If the condition of the barrel does not indicate that there was a blockage then it looks like an over charge or an inappropriate powder might have been used to create the load.

Just my two cents.

Add my two cents as well. barrel obstuction or over pressure round.

And I don't get your gun "expert" statement about "timing"? Does he mean it fired out of battery? Clearly it DID NOT fire out of battery...Your cartridge case is still in one piece (one mangled piece)...but out of battery firings are not at all like your experiance.

[AlaskanMBR]

I wasn't sure about that "timing" comment either, but at this point it certainly looks like overpressure is what happened. I'll be in touch with HSM today and I'll let you know how it goes...

Thanks for all your input guys! This has been a real learning experience for me.

[AlaskanMBR]

Oh, also, to answer your questions kennaquhair:

The ambient temp was roughly 65F, sunny with variable winds probably up to 15mph (I remember having to put big rocks at the bases of my target stands) The ammo was in my gun safe prior to being brought to the range.

Also, each of the points you made are good observations, I'll try to get a better pic up but you've seemed to nail it on the head.

The barrel is still in good shape, I can't see anything wrong with it.

[ftierson]

I agree that the cartridge case and bolt face look like an overpressure (whatever the cause) problem.

That means that the cocked hammer was probably caused by the bolt carrier (such that it is) re-cocking the hammer before returning the bolt to it's forward position but not having enough umph to rotate the damaged bolt into lug engagement.

Keep in mind that, while it's possible that the barrel is still fine, the barrel extension is likely to be damaged and need to be replaced...

Also, from the look of your other fired cases, it looks to me like the HSM ammo that you were firing (except for the problem round, of course) is a relatively mild load...

Forrest

[AlaskanMBR]

The lower is in fact trashed, as is pretty much all of the rifle. I wouldn't trust any critical parts that have gone through such a traumatic event. To me, the whole rifle is gone. SO sad...

Took one of the rounds apart and it was loaded at 23.8 grains. That load brought the powder to about 1cm lower than the shoulder of the brass. Not sure if that helps or means anything without taking a bunch apart and weighing them.

[kennaquhair]

1 cm below the shoulder? That would be enough. Sounds as though there was a hiccup on the line and a double charge was thrown. You probably ended up with a round with a compressed charge in it.

The powder column to the shoulder of a LC 01 5.56x45 case is about 3.2cm tall. There is enough free case volume above the 2.2cm tall, 23.8 grain powder stack that you described to create a passle of trouble without trying very hard.

If I had anything else to fire this ammunition through, I wouldn't. I imagine that the manufacturer is going to be interested in getting what is left of this batch back from you, and if they are, ship it back to them.

Let us know what the manufacturer does and if they leave you with the ammunition there will be plenty of suggestions as to how to deal with it.



edited to correct the worst of a really bad spelling day

[ammolab]

I am not following you guys too well.... 23.8grs of powder should just about fill a 5.56mm case to the shoulder, right. Do you mean one MM (millimeter) below the case neck?

One cm (centimer) below the neck of a 5.56mm case means it is about half full!

Don't know what powder you are talking about...but 23.8grs of any suitable propellant will not cause a pressure like illustrated.

[AlaskanMBR]

Roughly 5mm to 1cm below the neck, meaning a little over 3/4 full. That is just an eyeball estimate however, and we do not know at this point what powder was used. From what I've been told 23.8 grains should not be enough to overpressure, that is the measurement taken from one round of the ammo in question (we only took apart 1 round), certainly a good round. I did shoot ~500 rounds of this ammo through the rifle with no problems.

[ammolab]

"case neck"...you mean the mouth of the round? Not the lower part of the neck (where it meets the shoulder).

Your disected round (and the other 500) sound OK.

The sad thing is.....the round you need specs on....is the one that went - BOOM!

[ftierson]

Originally posted by AlaskanMBR
Roughly 5mm to 1cm below the neck, meaning a little over 3/4 full. That is just an eyeball estimate however, and we do not know at this point what powder was used. From what I've been told 23.8 grains should not be enough to overpressure, that is the measurement taken from one round of the ammo in question (we only took apart 1 round), certainly a good round. I did shoot ~500 rounds of this ammo through the rifle with no problems.

It all depends on the powder used...

23.8 grains of Bullseye would blow the gun completely up...

It sounds to me like they were using a H322 burning rate powder (or quicker), which is a little too fast for this load. If H335, 25-26 grains of it would have filled the case to the bottom, or a little higher, of the shoulder.

If the case was really only 3/4 full, the powder is too quick (assuming enough pressure to operate the gun, which it looks like was the case here)...

What does the powder look like? Ball, flake, tubular or other...?

Forrest

[ftierson]

Originally posted by ftierson
It all depends on the powder used...

23.8 grains of Bullseye would blow the gun completely up...

It sounds to me like they were using a H322 burning rate powder (or quicker), which is a little too fast for this load. If H335, 25-26 grains of it would have filled the case to the bottom, or a little higher, of the shoulder.

By the way, I should mention that my comment about H322 being a little too fast reflects my opinion. I would not use it, but many others do and are happy with the results.

However, I would certainly not want to use a powder that left the case only 3/4 full. If that was the case here, the powder would have needed to be pretty dense...

Forrest

[armed1]

I don't think your expert is much of an "expert". I have shined a timing light on my AR-15 many times during the night and it is always 3 after TDC>

The grains of powder is important, but so is the type of powder. You can easily put 27 or 28 grains of BLC2 into a 5.56 and it won't overpressure. Do the same with IMR 4895 and you'll have a blown primer at least.

I think you have a "case" for HSM to pay for your gun, no pun intended.

[AlaskanMBR]

Yeah, I wondered about the "timing" thing too, especially after we saw the brass that came out of the chamber...

I think you hit the nail on the head kennaquhair, the bolt most have been in battery for the brass to be blown out at the extractor depression like it did. That seems to make the most sense to me. Also, take a look at how the extractor is bent- it seems to be bent at the point at which it would be supported by the carrier when in battery. Notice where the carrier cracked- right at the point where the extractor would have been exerting force on it. Does this make sense??

I got the carrier and bolt out of the upper- still can't get them apart but the bolt will go back and forth a little bit, and the bolt cam pin seems to be intact. The carrier has a huge crack on the top.

Upon inspecting the bolt up close, I noticed that the brass imprinted the headstamp on the bolt face. You can't see it well in the picture, but it's there.

[AlaskanMBR]

Of course, where it cracked was the thinnest part of the carrier so that kind of negates that point...

[ftierson]

The more that I see, the more that I think that you were pretty lucky...

Apart from blowing up the gun, of course...

The fact that no one was injured speaks volumes about the safety features designed into the weapon.

Guns can be replaced, but eyes and foreheads can't...

Forrest

[AlaskanMBR]

OK - Got the bolt and carrier apart with a little wiggling.

Sandy from HSM didn't seem to care that I took it apart myself, and asked for more clear pics. I took some pics with a better camera and a magnifying glass. Check this out!!!

[Wil-C]

look at the crater around the firing pin indention on the primer, both that & the flattened shoulder on the primer are signs of extremely high pressure. This sure looks like a powder overcharge.

[mj2evans]

Sorry about your gun but glad you are ok........cool pictures.