Last trip to the range, the shooter on the next firing point to me blew up his AR.  It seemed to me that it was caused by a detonation before the breech was closed because clearly lots of gas was released into the receiver with no apparent damage to the barrel.

Ammo was factory.  No reloads.

You cannot believe the mess that it caused.  Upper was split at the rear where the charging handle locks up and lower was bulged severely in the magazine and less so in trigger area.  Sobering when you are firing an AR too.
Comments?

Pictures?

Wow. Post numbah one is certainly interesting....

Always wear eye pro at the range.  

Not your rifle. No pics. You want speculations.

ETA: Your second post should identify the brand of the other guy's rifle that went kaboom that was not shooting reloads. Yawn....

Maybe I am off base, but isnt the AR designed so that the firing pin is unable to strike the primer until the bolt has been locked?

You are correct.... but that doesn't mean that it is impossible.

Worst case scenario of a broken or not present cam pin? Or maybe a foreign object in the breech face? Or the most likely, a way too soft primer.

With an AR it takes some really bad luck to have an OBD.

Sorry,I've been laid up with surgery.    

The upper was an Adtek; however, there is nothing inherent in a upper that would cause a ka-boom.  Lower, trigger group, ammo, could contribute, but not upper per se.  No pics. kudude

What ammo was he using?

maybe headspace issue...guess he forgot to check with the FIELD gauge hah

Welcome to Arfcom.
AR-15  kaboom is, indeed unusual.

Welcome to the boards. Sounds like a builders error or just the 1/1000000 unfortunate occurrence.

Claiming a KB with no pictures or anything?

so how would it be then





 

I'd Like to see this!

Meh, almost been a couple weeks without a reported kaboom. Need pics.

Was the guy injured or was he okay?

I would be very interested to know what ammo he was shooting, especially if it was a soft nose bullet.

Don't sound like a factory round...only time I've heard this happen is with reload and the 1st bullet got stuck in the barrel and then the next round was fired.

Whatever the cause was, there is definately some sort of obstruction in the barrel...

dang sounds crazy.. buying my first AR today hope I dont get bad one or a bad round

We have had this discussion on the board before. It seems possible that a soft nose bullet can have the exposed lead nose catch on the feed ramps and cause the bullet to push into the case. That can cause a catastrophic overpressure situation and blow the case out.
The AR15 should not be able to fire out of battery according to people who know a lot more than I do.

We really need more details or this is just guessing.

First thing I do is snap pictures with my phone. I haveta call shenanigans. Pics or it didn't happen.

-sf

Agreed.

Too many possibilities to speculate.  Need more info and pics.

How would a bullet pushed into the case cause a detonation before the cartridge was chambered.  I though this was practically impossible with the AR design.

It can't, but the overpressure can blow out the case head. I don't think we ever came to a definitive conclusion based on what little info we have had on these incidents, but bullet setback can dramatically increase pressure. That would account for a lot of these kabooms where the barrel isn't bulged like from a bore obstruction. Many lately have had the upper receiver blown apart- with other damage.

A bullet pushed in during loading can and will cause an extreme pressure and blow the case out at the web. I have seen several ka-booms in ar rifles and when you see the case it looks like it was fired out of battery. What i have heard is that it didnt fire out of battery but the cartridge was loaded hot or had the bullet shove in while being chambered and in the shorter gas systems the cartridge was actually starting to extract while the chamber was still overpressure. I dont know if that is true but i have seen at least 5 cases where they blew out just forward of the web and you could clearly see the case was unsupported and expanded till it ruptured. I have looked at bolts and if everything is in good working order you can start to push the bolt in and check firing pin protrusion and it will not protrude from the pin hole till the bolt is rotated making a cartridge fire out of battery almost impossible with an undamaged bolt and carrier.

My KB was with a factory load with a soft point...a buddy of my had the same thing happy with his bushy and a SP...I'd really like to know what type of ammo was used...SP may be a thing to think about avoiding in the future...

FYI

I did not take pics because I was closing down and leaving when the incident occurred and I was under a time constraint.  
I realized there was a kaboom because the shooter and his buddy were dealing with a slight cut to shooters trigger finger.
Ammo was factory Federal or Winchester (shooter said he was shooting both, and at the time I left they had not gotten into the receiver to check.  Therefore I also don't know if there had been a failure to eject or some kind of double feed.  

Like so many of you, I understand AR's cannot fire unless locked up.  I have experienced this condition with trash in chamber.  

The rifle was the shooter's target piece and looked as if it had  been previously shot, but was in good condition vis a vis externals less ka-boom damage.

I have built ars; installed several different aftermarket triggers and the only condition I think could cause the problem if loads were factory  and head space was right would be a failure to extract prior to a load causing a slam fire or a compression detonation upon stuffing the bullet into the case.  (That is a novel cause, but I have heard of people doing it trying to drive a loaded stuck case out of a bolt gun.)

Although the shooter was not badly injured, the rifle was trashed: upper rear split at charging handle and lower bulged at mag well and trigger position.

Sorry I did not get pics (I'd have felt real uncomfortable photoing a fellow shooter's ka-boom even if I had had time to take pic's).  

I've seen several M-1's blown in this fashion, but this was my first (and I hope my last experience with an ar.)  

And as someone pointed out, i t could have been a 1 in a million event which I hope it was really.  

I do know this:You can be sure I will be testing my loaded ammo in a case gauge before firing and keeping my extractor clean and functioning and chamber clean.

Kudude

When improperly loaded ammo is the cause, 99% of the time it is due to an undercharged round, not an overcharged one.  Undercharging is far easier to do than overcharging. Remember, most firearms are factory tested with proof rounds, overcharged rounds that test the firearm's ability to safely handle pressures larger than found in normal operation.

When a primer ignites the powder in a normal, "healthy" round, the first order of business in that millisecond is to uncork the bullet from the case. Gas pressure pushes the relatively loosely-seated bullet into the barrel -and continues pushing- thus allowing the volume to increase. The conflagration is contained. The pressure inside the case is minimized from the beginning and keeps reducing as the event unfolds.

When there is not enough powder in the case, that empty space interrupts the timing of the normal pressure curve allowing more pressure to build inside the case than can be contained or properly vented by the bullet's passage down the barrel.  The gas expansion gets a head start and grows to overcome the otherwise controlled process. The bullet is popped, but that is not enough to alleviate the greatly excessive pressure behind it and the gas finds the "escape hatch";  right through the case at the extractor gap in the bolt head

A undercharged round has the exact same effect as an obstructed bore, but an obstructed bore will leave more evidence of itself.

So how would you explain subsonic rounds using ball powder? Would they not create excess pressure and technically be faster than full powered loads?

this sounds like BS, I've shot thousands of soft point rounds without any problems

Pictures or it didn't happen.

That sucks... luckily everyone was ok?

x2








 

Based off what I read here, this kind of thing happens daily unless you own a Colt or Noveske.  No big.

EDIT: New information

Not sure why you would say that since we had a recent thread a few months ago where a Colt blew up. Typically ammo.