AR-15 kaboom (link provided)


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Timmypage16
March 26, 2012, 10:27 PM
The link below has an interesting discussion talking about a kaboom in an AR-15. I would enjoy some of your guy's opinion on it. This is not my post, but I stumbled upon it reading on the ar15 forums.

I think that it was caused by an obstruction of the barrel. Based on the description provided, one of the failure to fires could have been a squid load causing the barrel to be obstructed resulting in the next round to cause the kaboom. This is the only reason why I think that they were able to recover a bullet from the barrel.What do you think?

http://www.ar15.com/forums/t_3_118/568580_KABOOM___what_do_you_think_happened_.html

Tim

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Otto
March 26, 2012, 11:10 PM
There's no bulge in the barrel so I'd rule out obstruction.
Most rifle powders fill .233 cases up to the top of the neck so I doubt it's an over charge.
My guess would be out-of-battery discharge.
This is why I don't shoot other peoples reloads and I bet this guy won't either from now on.

animator
March 27, 2012, 12:17 AM
Out-of-battery fire, which would be difficult to accomplish in an AR.. or case failure at the web.

blarby
March 27, 2012, 12:35 AM
OOB wouldn't necessarily cause a case head detonation. You would probably have a discharged cartridge. ( the bullet would be out of the brass )

This is probably case failure.

However, the bullet copper transfer onto the feed indicates there may have been ignition and shock with the round ON the feed, not in chamber, and in a weird angle, I might add.

Unless he loaded it with pistol powder ( which I doubt, as they fired 494 of them previously) it would be hard to charge a case to this level with rifle powder.

Check your brass.................... this is one of the many reasons.

It is however possible that it slammed/fed sideways, struck the primer, and ignited OOB... releasing the pressure with the bullet pinned against the frame/slide rail, and venting through the weak point in the brass.

Thats a toughy...maybe someone better versed in the platform can help.

animator
March 27, 2012, 01:12 AM
Looking at it a bit closer, you can see where the head flowed into the ejector opening on the bolt face, so it was definitely some high pressure involved.


Another speculation would be the case failed to fully feed, and the bullet got jammed further back in the case prior to fully chambering, creating the catastrophic increase in chamber pressure when the round fired.

evan price
March 27, 2012, 01:35 AM
1. Contaminated powder (mixed powders- fast pistol powder got left in the powder measure) maybe.
2. Weak neck tension on the brass, the round nosed into the feed ramp and the bullet slid nearly all the way into the case when it chambered, making a very compressed load.

The side of the bullet looks like it was deeper in the case than just to the cannelure-
However, what's caused that ring about 2/3 of the way down the nose of the bullet?

Timmypage16
March 27, 2012, 08:07 AM
I believe that ring on the bullet was from the rod they used to pound it out of the barrel.

MtnCreek
March 27, 2012, 08:24 AM
Just a thought on the bullet pushed back: I used to shoot commercial reloads from a local source. A friend and I went in together on a couple thousand .223/55gr FMJ’s. Both of us had many bullets pushed back into the case to the point where powder could escape between the bullet and case neck. I had unloaded my chambered carbine several times to find a cartridge like this in the chamber. I have little doubt that both of us most likely fired a cartridge (or several) with the bullet pushed in. I’m not saying that it could not or would not cause a major overpressure, just saying that I <Think> I’ve shot a cartridge in that condition w/o a KaBoom.

steve4102
March 27, 2012, 08:48 AM
The offending bullet was still in the barrel!
Classic sign of a barrel obstruction.

243winxb
March 27, 2012, 08:58 AM
Obstruction like Steve said. http://i338.photobucket.com/albums/n420/joe1944usa/Firearms%20%20and%20%20Reloading/KABOOM/th_PA-15-5.jpg (http://s338.photobucket.com/albums/n420/joe1944usa/Firearms%20%20and%20%20Reloading/KABOOM/?action=view&current=PA-15-5.jpg)

jerkface11
March 27, 2012, 09:58 AM
Several rounds that did not go off followed by one that went off out of battery. That says one thing to me HIGH PRIMERS.

Superdave70_02
March 27, 2012, 10:46 AM
Maybe he loaded a soft pistol primer loaded high that got set off by the bolt face?

I was also wandering about maybe not cleaning out the powder hopper good and getting some fast pistol powder on the first couple rounds.

snuffy
March 27, 2012, 11:12 AM
Several rounds that did not go off followed by one that went off out of battery. That says one thing to me HIGH PRIMERS.

Impossible! The brass showed a normal firing pin dent in the primer. The AR-15 platform will not allow the firing pin to protrude far enough to make that normal looking firing pin dimple WITHOUT the bolt being completely rotated into battery.

Most .223 powders run at nearly 100% load density. That means there's no room for the bullet to be pushed back to account for increased pressure for a deep seated bullet. Besides, deep seated bullets in rifles is NOT the same as straight walled pistol/handgun ammo.

My guess is one of the no-fire previous rounds spit it's bullet out of the case under primer power. It's possible 2 bullets were stuck in the barrel. The next round, the one that blew, tried to push the obstruction out. What most fail to realize is; there's air trapped between a bore obstruction and the oncoming bullet fired by the next round. The trapped air has to raise in pressure enough to move the bullet/obstruction. This usually causes a barrel bulge, or sometimes a burst barrel.

In this case, the case head blew before the second bullet could exit the barrel, relieving the pressure, allowing the bullet to stop.

I think a bore scope examination of that barrel would show where a bullet stopped ahead of where the recovered bullet stopped. It might also show a bulge that can't be felt on the outside.

We may never know for sure. But one thing I do know, blaming reloads is NOT the right answer. Taking care while reloading any ammo will result in good ammo and safe shooting. Yes, there's some that should NOT ever consider reloading, perhaps that's what happened here, somebody with the mindset of get it done, don't bother me with details.

sugarmaker
March 27, 2012, 11:26 AM
Sure looks like an obstruction to me - extreme copper fouling after 500 rounds? With those kinds of pressure signs on the case the bullet should exit if the bore were clear. Max charge of temp sensitive powder sitting in a hot barrel for too long?

Clark
March 27, 2012, 11:39 AM
animator

Out-of-battery fire, which would be difficult to accomplish in an AR.. or case failure at the web.

I have blown up lots of guns in experiments and have lots of overloaded cases from ARs that never hurt the AR.
I was going to post that there does not seem to be much pressure, just a failed case where there should have been case support by the chamber.
The resultant gas cutting makes are real mess of some secondary failures.

Glad to see someone else figure it out.
I was starting to worry about the internet.

popper
March 27, 2012, 12:15 PM
OOB is easy to get in AR. Firing pin floats and sometimes sticks. I suspect inspection error and case failure.

MEHavey
March 27, 2012, 01:28 PM
Firing pin floats and sometimes sticks...
That I have not seen before in an AR.
Any citations/causes/occurances that readers know of?

ClickClickD'oh
March 27, 2012, 02:52 PM
OOB is easy to get in AR. Firing pin floats and sometimes sticks.

AK and SKS yes, AR? Unless you have some sort of telescoping firing pin in your AR... not so much.

joustin
March 27, 2012, 03:30 PM
Would need a magic or really long firing pin for it to protrude beyond the bolt face before it cam's and locks in the chamber.

Sent from my Kindle Fire using Tapatalk

steve4102
March 27, 2012, 03:45 PM
I was going to post that there does not seem to be much pressure, just a failed case where there should have been case support by the chamber.
The resultant gas cutting makes are real mess of some secondary failures.

Even with a failed case the bullet would have exited the barrel, which it did not.

Clark
March 27, 2012, 07:29 PM
steve4102

I was going to post that there does not seem to be much pressure, just a failed case where there should have been case support by the chamber.
The resultant gas cutting makes are real mess of some secondary failures.
Even with a failed case the bullet would have exited the barrel, which it did not.

The start pressure for a jacketed 223 jacketed bullet is ~ 2000 psi.
I can imagine it going either way, but I have not tried it.

MtnCreek
March 28, 2012, 08:32 AM
Educate me please. Unless I’m reading this wrong, some are saying a simple case failure could have caused this, correct? If so, please explain to me how this works. There’s an experienced handloader here that says he typically loads his brass till head separation. So he has a load within safe spec’s and on the last firing, head partially separates. If this AR explosion is the result of an otherwise safe load, but with weak brass, why all the damage?

Thanks!

steve4102
March 28, 2012, 08:47 AM
Because there was an obstruction in the barrel.

The offending bullet did not exit.

If it were any of the following, over pressure, weak brass, out-of-battery, slam-fire, high primer or any other scenario except an obstruction the bullet would have exited. It did not.

Barrel Obstruction.

Clark
March 28, 2012, 12:12 PM
These are 223 brass I fired with case support.

The OP pic brass shows less pressure.

I don't know if the OP was barrel obstruction or out of battery, but I am leaning toward out of battery.

MtnCreek
March 28, 2012, 12:19 PM
Clark,

That's case on the right looks Nasty! What were they fired in?

Thanks!

Clark
March 28, 2012, 03:10 PM
Ruger #1 or Ruger #1V

That is Blue Dot 33 gr Vmax and 4200 fps.
The same load sometimes shows no pressure sign and 4100 fps.
Some peaky powder.

I do not recommend Blue Dot for high pressure as useful loads, just interesting.

steve4102
March 28, 2012, 05:52 PM
Clark, your bullets did exit the barrel, correct. In all of your experiments and way over pressure loads, have you ever had a bullet not exit the barrel and still blow up the gun?

Has anyone had a true Out-of-Battery fire that the bullet did not exit the barrel?

Clark
March 28, 2012, 06:40 PM
No.
And I have never done an out of battery experiment, either.

Jim Watson
March 28, 2012, 07:13 PM
I am not an AR guru but will note that guns I have seen that were shot with stuck bullets or other barrel obstruction have bulged or ruptured barrels but normally intact actions. Contrariwise, guns shot with gross overloads, wrong powder, weak brass, or other source of high pressure gas release, tend to have demolished actions but barrels that look like they could be put on a new receiver and reused.

I was once on a range waiting for the XTC guys to get done so the LR shooters could bed down, when not one but two ARs came off the line with blown cases. Damage to the guns was light to moderate and the shooters were not hurt. Both rifles were assembled in the same shop and the ammo for both loaded in the same setup. I don't think anybody there reached a firm conclusion but there was something devastating in common that day.

steve4102
March 28, 2012, 07:23 PM
I am not an AR guru but will note that guns I have seen that were shot with stuck bullets or other barrel obstruction have bulged or ruptured barrels but normally intact actions. Contrariwise, guns shot with gross overloads, wrong powder, weak brass, or other source of high pressure gas release, tend to have demolished actions but barrels that look like they could be put on a new receiver and reused.

I was once on a range waiting for the XTC guys to get done so the LR shooters could bed down, when not one but two ARs came off the line with blown cases. Damage to the guns was light to moderate and the shooters were not hurt. Both rifles were assembled in the same shop and the ammo for both loaded in the same setup. I don't think anybody there reached a firm conclusion but there was something devastating in common that day.

Did either one of these instances/scenarios result in the bullet still in the barrel?

Jim Watson
March 28, 2012, 08:10 PM
Not in any I have seen in person.
Who knows what gets posted on the internet.

steve4102
March 28, 2012, 08:31 PM
Then it looks like we are back to a barrel obstruction .

Timmypage16
March 28, 2012, 08:39 PM
Do you think it.could be a combination of case failure and obstruction? Could the barrel have been obstructed and the path of lease resistance be the case failure? This would result in a bullet sticking in the barrel and the barrel not being destroyed.

steve4102
March 28, 2012, 08:51 PM
Only if the obstruction was just inside the throat where the offending bullet contacted the obstruction when chambered. Doubt it, he had squibs, fired over them without checking.
Barrel obstruction.

provoartkaa
March 30, 2012, 02:51 PM
could it have been a hang fire. such as a light firing pin strike and while removing the case and bolt from the barrel the round went off?

TripodXL
March 30, 2012, 07:02 PM
I would humbly disagree with the premises expounded so far. First, it is fundamentally impossible to have an OOB ignition in an AR. If you don't understand that, then you don't really understand how the AR works, with all due respect. I have yet to see a RIFLE barrel that was fired with an obstructed bore that wasn't ruptured. Most people that were not in the military don't know how to properly clean the BC, the bolt itself and the locking lugs and even those that know better often don't as it is a PITA. Most people hose it out with something and pull a boresnake through it and call it good. I went to photobucket and looked at the 4 pics there and also read the statement. I had to think about it for quite a while but when you understand the full mechanics of the AR, have a lot of experience (I'm old) and are a reloader, it makes sense. I think this is a case of "tolerance stacking" and the following explains why. In normal operation with the rifle held up in the firing position the extractor (internally, closed on a round) is at the 2 o'clock position (area in front of the dust cover). The extractor is the weakest part of the bolt lockup on a cartridge in battery (IB). The verbage said that there had been several fail to fires just before this took place and assuming (yes, I know, but you have to make some) the shooter was not a COMPLETE idiot and the FTFs were still complete rounds when removed, here's my take on the event. They had fired 494 rounds out of 500 and who knows how many the previous time the rifle was shot, and human nature being what it is (lazy) and probably not having the rifle properly cleaned was ONE of the causes of the problem. The other part is software error. First the FTFs were probably caused (IMHO and 33 years of military service) by a very dirty BCG and the FP hole had so much crud in it that it wouldn't fire a few rounds until it was knocked out and this would further support my contention of a dirty rifle. Next, not a single person questioned what caliber this AR was chambered in!!!!!? You can get them chambered in .223 instead of 5.56x45. Now typically this is not a big problem...typically. Now say you have a very dirty AR and some combination of the following, .223 chamber, military brass and/or brass that was too long (over spec). If the BCG goes to battery (and it does so robustly) you now have a bullet that is pinched ahead of the chamber because the headspace is too tight. Normally when an AR is fired the bullet goes down the bore and when it reaches the gas port the gas blows back the BC (gas impingement, GI) until it pulls the bolt out of battery and the remaining gas pressure pushes the bolt face back into the ALREADY moving BC and the entire BCG moves back into the loving arms of the buffer and spring assy. This did not happen. The picture of the bullet shows the ring on the ogive from the cleaning rod used to remove it. It has soot on it ahead of the cannelure from blowby gases (blowby happens with every bullet fired watch one in slo-mo) highlighting the rifle engraving where the bullet was pushed into the rifling. The round went off and overpressured the receiver ring and caused the case rupture at the extractor position, blowing it off. The rupture is very specific, if it had been an OOB ignition it would have ruptured in a longitudinal direction or more generally around the head of the cartridge causing some head separation. The damage to the UR in front of the dust cover confirms this. The over pressure FORCED the bolt open and slammed it into the BC causing it to "flower" since the GI system had not functioned (the bullet basically remained stationary and became a plug, no gas no GI cycle) and started the BC into backward motion thus "softening" the recoil of the bolt as intended. The now deformed bolt was sent backward under high pressure and basically destroyed the UR since it no longer fit the insides of the UR. This sequence of events would account for the broken extractor and matching damage in front of the dust cover on UR, the "flowered" (sic) BC and the corresponding fact that the GI system did not work, the fact that the barrel is not ruptured, the fact that you still have a pristine bullet, the fact of the VERY specific case rupture matching (accounting for) the broken extractor. This is the only circumstance that accounts for everything. The BC being AFU was what was hard to figure out. If it had been an obstructed bore, I don't think it would have damaged the BC so badly if at all. This was caused by a very overpressured round, to such a degree that it's not achievable with an overloaded round. The BC is made of solid billet steel!!!! In 33 years and a lot of civilian ones I have never seen a BC destroyed. Bolts yes, but not BCs. Improperly loaded ammo (LOA) or wrong ammo (.223 vs 5.56) or combination thereof, is what caused the explosion and make no doubt, there was an explosion. This is MHO of the event. The man is lucky he wasn't shooting from the standard position. Be well and enjoy.

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