AR-Kaboom

[bgarman47]

Another cause, though somewhat unlikely, could be the system is grossly over gassed, and/or have an improperly cut chamber.

If the barrel is a carbine length gas port location with a particularly large gas port size (something like 0.075"+), especially if that barrel is 14"+ long, primary extraction may begin while the case is still holding residual pressure. This can result in case head separation.

This is usually seen in rifles who's bolts have the black O-ring in the extractor assembly specified by NSW Crane, as it makes it very difficult or impossible for the extractor to jump the case rim.

This problem arises more with cheaper rifles & barrels. Usually the cause is a concert of errors. Oversized gas port resulting in increased gas flow. Short "commercial" spec (0.4636") headspace combined with a short barrel lead resulting in the projectile sticking in the rifling increases chamber pressure initially. Usually these rifles also have a standard carbine or maybe a H1 buffer which doesn't help matters much.

Basically the most likely culprit is a combination of several out of spec parts leading to a dirty and tight chamber, higher than average chamber pressure, higher bolt velocity, and case head separation. I could go into more detail on at of these points individually, but this is already a long post.

I do not believe the admittedly poor shooting technique to be at fault.

 

[edwea]

I'm thinking more like a firing pin being stuck. If it doesn't float freely in the bcg, it could be firing off the primer before going fully into battery.

 

[ECS686]

Scanning through I didn’t see.
Were the guns home builds???
And was his “factory ammo” from a guy selling “his reloads” at a gun show or unknown internet origin???

Also, Downward pressure on a magazine shouldn’t cause any issues. Especially a major KB! A lot of folks use the magazine as a monopod and it doesn’t cause the jams like DI’s said it would in the 80’s

 

[Titanium_Frost]

Scanning through I didn’t see.
Were the guns home builds???
And was his “factory ammo” from a guy selling “his reloads” at a gun show or unknown internet origin???

Also, Downward pressure on a magazine shouldn’t cause any issues. Especially a major KB! A lot of folks use the magazine as a monopod and it doesn’t cause the jams like DI’s said it would in the 80’s

It was stated to be a factory Sig firing range provided Federal American Eagle .223 ammo.

Which makes the event quite the statistical anomaly given the apparent quality of the objects in question. Certainly the OP can infer that "AR Kabooms" are exceedingly infrequent despite the subjects apparent common experience with them.

There is some mitigating factor you are not seeing here with his rifle. Quite unusual in my experience.

Also as an aside, the "magwell technique" has been taught in classes in my neck of the woods for a long time, never to my knowledge has it led to a kaboom. I am not defending nor am I a proponent of the grip technique, just stating my experience with it.

 

[Leo]

I shot high power matches, every weekend from May to October across the Midwest for 7 years. 100's of thousands of rounds, by 100's of competitors, most shooting the AR chassis rifles.

Exactly one AR blew up, and that was quickly solved as an inexperienced reloader used a case full of WW296 magnum pistol powder instead of the proper WW748 medium rifle powder.

For a single man to have blown 4 rifles with factory ammo, there has to be something that is exactly centered around him, nothing else is statistically possible. The AR is a pretty reliable design proven over decades.

edwea has a possible answer, but what kind of routine would stick 4 firing pins, and break cam bolts?

 

[Ark]

If you know a lot of AR shooters, you probably still don't know 4 people that have had "kabooms", much less one guy who has had 4. Operator error at some level is indicated.
Maintenance / cleaning issues? Headspace correct?
Barrel properly torqued/aligned with barrel extension?
BCG assembled correctly?
Some behavior of his is the culprit IMO. I've seen shooters hold at the magwell before. Usually they claim to prefer the vertical orientation, similar to the pistol grip, but more likely they lack proper conditioning, and their arm gets heavy being held extended in front of them.
Regardless, I've never seen that technique, alone, cause a kaboom, but it could maybe, possibly be a contributing factor.
I don't think we're gonna know the answer to this, without a thorough post mortem, or until he has number 5.

If there was a way to put your hand on an AR and make it explode, some time in the last 60 years we'd have found out about it.

 

[Ziggidy]

Interesting thread. I am not a gunsmith or anything close to an expert when it comes to any gun. I wonder if it was the same gun manufacturer with each of the 4 kabooms?

If it was the same, why does he keep going back to that brand?
If it was not the same, he needs to definitely and see what he is doing wrong.

I certainly would not stand near him while he is shooting an AR, and possibly any other; seriously. If his problem is man made, what is he doing and can it affect his other guns? Sounds harsh, but one of these times he (or others) may not be so blessed.

If he still has the other kaboom rifles, he should take them to a good gunsmith and possibly learn what’s happening.

 

[Ziggidy]

What kind of lube / grease is he using, and how much?

Is it possible he’s using 5.56 in his 2.23?

 

[Expat]

If this happened as described, I would assume Sig and Federal have been informed and the gun is on its way to one of them. Sig is usually all over any alleged gun issues causing a kaboom.

 

[Kirk Freeman]

Forward assist use?

 

[patience0830]

Another cause, though somewhat unlikely, could be the system is grossly over gassed, and/or have an improperly cut chamber.

If the barrel is a carbine length gas port location with a particularly large gas port size (something like 0.075"+), especially if that barrel is 14"+ long, primary extraction may begin while the case is still holding residual pressure. This can result in case head separation.

This is usually seen in rifles who's bolts have the black O-ring in the extractor assembly specified by NSW Crane, as it makes it very difficult or impossible for the extractor to jump the case rim.

This problem arises more with cheaper rifles & barrels. Usually the cause is a concert of errors. Oversized gas port resulting in increased gas flow. Short "commercial" spec (0.4636") headspace combined with a short barrel lead resulting in the projectile sticking in the rifling increases chamber pressure initially. Usually these rifles also have a standard carbine or maybe a H1 buffer which doesn't help matters much.

Basically the most likely culprit is a combination of several out of spec parts leading to a dirty and tight chamber, higher than average chamber pressure, higher bolt velocity, and case head separation. I could go into more detail on at of these points individually, but this is already a long post.

I do not believe the admittedly poor shooting technique to be at fault.

But. . .but. . .4 times?

 

[patience0830]

Is ANYTHING consistent through the 4 kabooms besides the rifle driver?

 

[edwea]

Is ANYTHING consistent through the 4 kabooms besides the rifle driver?

Improper maintenance?

 

[chuckp]

Four different rifles and they all were fed the same ammo when they blew up?

 

[bgarman47]

After taking the time to read some more responses here and properly caffeinating my brain, I'll offer this...

My initial post was made under the assumption this was simply a case head separation. I missed the mention of a broken cam pin.

In my experience, cam pins are quite durable. Although not as hard as the carrier itself, they are still quite difficult to break. In fact, I've only seen 3 types of events that break cam pins:

Improperly loaded ammunition containing pistol powder

A squib followed by live ammunition

300BLK in a 5.56 Rifle

The latter being the most common, and in my opinion, the most likely.

Group shooing sessions often have one table set aside for loading of magazines. Is there any chance, however slight, that a round of 300BLK could have been introduced into a magazine?

As others have mentioned and is worth repeating, catastrophic failures are rare. Very rare. For the same individual to have experienced several is so statistically unlikely as to be nearly impossible. Unless human error is involved.

 

[daddyusmaximus]

On the bright side...

Props to the church for having a security team... and for them... taking time to train.


That begs the question...

Did he transition to his sidearm after the kaboom, and finish the drill?
This could have happened during a fight.

 

[Titanium_Frost]

On the bright side...

Props to the church for having a security team... and for them... taking time to train.


That begs the question...

Did he transition to his sidearm after the kaboom, and finish the drill?
This could have happened during a fight.

Hmm. Train how you fight I suppose but how many training agencies and/or ranges would actually recommend or allow something like this to happen?

 

[BGDave]

The only relevant question is "does he own a .300BLK?".

This guy knows. Someone there owns a .300BLK for sure.

Dip stick that barrel and see how far the "noodle" made it.

4 times ? Same rifle or 4 different rifles ?

I don't think I'd want to be around this cluster .

 

[johntheplinker]

Does he like to tinker with his rifles, maybe trying to improve the trigger pull and ending up with an occasional hammer follow?

 

[DoggyDaddy]

Hmm. Train how you fight I suppose but how many training agencies and/or ranges would actually recommend or allow something like this to happen?

Yeah, I'm thinking a hot long gun range would be a place where you'd be ill-advised to run downrange firing your sidearm at your target.