Blew up my AR today. KABOOM!

Evil_Edie said:
i doubt that thats the cause considering the bolt is locked up. also in most cases i would think if it had fired out of battery the user would know right off the bat just due to the difference in timing at which he was pulling the trigger and the out of sync kaboom.
Click to expand...

If this was an OOB explosion, he would have known immediately because he would have been picking the bolt out of his forehead. An OOB explosion turns the rifle into a blowback system which it was not designed to accommodate. Consider the amount of energy involved in this simple case head failure which occurs with the bolt locked up. Now multiply that energy release by maybe 1000 times and imagine what kind of havoc that would involve.

I also don't think a squib load would have cause this. If that were the case the barrel would have exploded considering the fact that the metal is thinner at the barrel than at the chamber .
Click to expand...

A squib load doesn't automatically result in a burst barrel. It can but it doesn't always happen that way. There are numerous examples of multiple bullets being caught inside a barrel. I have two AR15 barrels that have bulges in them from stuck bullets.
 
C77 said:
Fix the barrel in a padded vice with the receiver upside down. Use a large brass drift and a hammer to strike the carrier at the back (where the auto sear would engage if it were auto) to drive it rearward. This will force the cam pin to turn the bolt. Your locking lugs are still engaged, and your extractor is most likely bent and jamming the carrier.
Click to expand...

+1. This is what I had to do to get mine apart. You may have to whack the carrier pretty fricken hard to drive it to the rear as the extractor will be tightly jammed into the barrel extension.


The photos of your rifle and your case and your post are perfectly consistent with a case annealed incorrectly. The case failed and the pressure blew out the case head.
Click to expand...

While annealing is a potential cause it could just be a case that ended up with a thin section around the case head from the drawing process. With hundreds of millions of cases produced annually, errors will occur. The soot blackening around the neck and shoulder of the case is quite odd though.
 
Thank you for the advice so far. Tonight I will try again to free up the internals which are jammed in there quite badly.
I doubt I will be able to save much but I do not want to destroy the evidence in case the place I bought it from wants it back.

This rifle previously had NO function issues whatsoever and spent cases were usually pretty clean. That round may have been a symptom of a much larger problem about to occour.
 
Suputin said:
+1. This is what I had to do to get mine apart. You may have to whack the carrier pretty fricken hard to drive it to the rear as the extractor will be tightly jammed into the barrel extension.




While annealing is a potential cause it could just be a case that ended up with a thin section around the case head from the drawing process. With hundreds of millions of cases produced annually, errors will occur. The soot blackening around the neck and shoulder of the case is quite odd though.
Click to expand...

A thin case would also look much like this, but would be less likely in a new round based on how the brass is cupped and drawn over a mandrel. The entire web would have to fail to get this result would be my guess.

The blackened case mouth is consistent with upside down annealing. If the case head was soft it could fail exactly as described here. If the the case head was too soft, and the case was annealed upside down, then the case mouth would be too hard.

If the case mouth was too hard, it would not expand as quickly or as much as it should to obturate the chamber. This would explain the gas and heat travelling backward and blackening the case mouth.

(Further to that, I've measured a bunch of these norinco rounds and found them undersized by several thou)

I pulled one apart last year that was identical. No bulges or evidence of obstruction on a bore scope. All parts in spec. Bolt still locked and the last point of support was fully forward, headspace was in spec as measured from that. Same blackened case mouth.

The other time I have seen blackening is when the flash hole was not punched through complete and small hard slugs from the rear were left inside the case, and then in the chamber. Operators would then force the next FTL closed with fwd assist and as a result puncture the soft brass at the shoulder with the hard brass slug from the flash hole. The result was no obturation and minor breech explosions. same blackened case.
 
C77 said:
A thin case would also look much like this, but would be less likely in a new round based on how the brass is cupped and drawn over a mandrel. The entire web would have to fail to get this result would be my guess.

The blackened case mouth is consistent with upside down annealing. If the case head was soft it could fail exactly as described here. If the the case head was too soft, and the case was annealed upside down, then the case mouth would be too hard.

If the case mouth was too hard, it would not expand as quickly or as much as it should to obturate the chamber. This would explain the gas and heat travelling backward and blackening the case mouth.

(Further to that, I've measured a bunch of these norinco rounds and found them undersized by several thou)

I pulled one apart last year that was identical. No bulges or evidence of obstruction on a bore scope. All parts in spec. Bolt still locked and the last point of support was fully forward, headspace was in spec as measured from that. Same blackened case mouth.

The other time I have seen blackening is when the flash hole was not punched through complete and small hard slugs from the rear were left inside the case, and then in the chamber. Operators would then force the next FTL closed with fwd assist and as a result puncture the soft brass at the shoulder with the hard brass slug from the flash hole. The result was no obturation and minor breech explosions. same blackened case.
Click to expand...

There's no need for all of this technical competence and logic, it's a Norinco.
 
Okay!
Just got back from the shop and it took a heck of a beating with a ball peen hammer and a punch to get the bolt out.

The bolt still rotates back and forth, firing pin is free. Cam pin, retaining pin, gas key all is as it should be.
Barrel looks fine except for the mess at the chamber end.

There was a spent casing in the chamber that will explain a lot. Came out as 5 pieces of brass. The mouth and body of the casing looks great! Color is just off a little. The back end of the casing is a total mess. Deformed, stretched and burnt black around the primer. Part of the base of the shell was blown out through the extractor. What I thought may have been broken pieces of bolt lugs were actually small pieces of the extractor crushed into the works. Even found half a primer cup.

I will post pics tomorrow. It has been a long day.
 
Rust said:
Okay!
Just got back from the shop and it took a heck of a beating with a ball peen hammer and a punch to get the bolt out.

The bolt still rotates back and forth, firing pin is free. Cam pin, retaining pin, gas key all is as it should be.
Barrel looks fine except for the mess at the chamber end.

There was a spent casing in the chamber that will explain a lot. Came out as 5 pieces of brass. The mouth and body of the casing looks great! Color is just off a little. The back end of the casing is a total mess. Deformed, stretched and burnt black around the primer. Part of the base of the shell was blown out through the extractor. What I thought may have been broken pieces of bolt lugs were actually small pieces of the extractor crushed into the works. Even found half a primer cup.

I will post pics tomorrow. It has been a long day.
Click to expand...

Any pics?
 
Rust said:
Okay!
Just got back from the shop and it took a heck of a beating with a ball peen hammer and a punch to get the bolt out.

The bolt still rotates back and forth, firing pin is free. Cam pin, retaining pin, gas key all is as it should be.
Barrel looks fine except for the mess at the chamber end.

There was a spent casing in the chamber that will explain a lot. Came out as 5 pieces of brass. The mouth and body of the casing looks great! Color is just off a little. The back end of the casing is a total mess. Deformed, stretched and burnt black around the primer. Part of the base of the shell was blown out through the extractor. What I thought may have been broken pieces of bolt lugs were actually small pieces of the extractor crushed into the works. Even found half a primer cup.

I will post pics tomorrow. It has been a long day.
Click to expand...
It sounds like the guys pointing fingers at the ammo were right, no?

Scary stuff.

Glad you weren't injured.

I wonder who the importer of the ammo was, and what their responsibility is, if any. I for one will continue to avoid bottom of the barrel ammo. My health and my firearms are worth a bit extra cost.
 
Power Pill said:
Glad i didn't buy any of that norinco ammo
Click to expand...

This can and has happened to every ammmo mfg in history, LOTS of kabooms in the U.S. It's not a failsafe procedure.

Considering the number of KB's related to Norinco ammo and the the number related to american ammo, I feel pretty darn safe shoting Norinco ammo.
 
Dietz said:
This can and has happened to every ammmo mfg in history, LOTS of kabooms in the U.S. It's not a failsafe procedure.

Considering the number of KB's related to Norinco ammo and the the number related to american ammo, I feel pretty darn safe shoting Norinco ammo.
Click to expand...
Can you point to info on catastrophic failures like this with US manufactured ammo?

I'm sure it has happened, but my Google fu must be weak. I can't find any more than a handful of accounts of such catastrophic failures with factory ammo, and most seem to be the result of squib loads that preceded the firing of a normal cartridge.

I'm genuinely interested in knowing how common such things are.
 
Dietz said:
This can and has happened to every ammmo mfg in history, LOTS of kabooms in the U.S. It's not a failsafe procedure.

Considering the number of KB's related to Norinco ammo and the the number related to american ammo, I feel pretty darn safe shoting Norinco ammo.
Click to expand...

There is no doubt that this incident was the ammo.

I have also seen this type of thing with US made ammo, but there are differences worth noting.

I know the reps and am confident in the laws in the jurisdiction where the ammo is made. I've even seen big name ammo manufacturers pony up for repairs and replacement. I've toured ammo factories and I've met their engineers. I've seen the QC lines, the scales and the optronic sensors. I've seen recalls posted. Every year the larger factories add technology to the QC lines because of consumer and legal pressure.

This drives the cost of ammo upward, then the opposite thrifty pressure to push down the cost of ammo gets cheap ammo on the market. This has not had a positive impact on quality.

Ammo is relatively cheap, with components costing pennies. Fire enough ammo and you will find a flaw eventually. But cheaper ammo made offshore is not worth the risk in my opinion. I've seen more incidents with this stuff in the short time it's been showing up on my ranges than with all the others combined. Everything from dud rounds, squibs, blown primers, key holing, bulged cases, and at least two breech explosions.

I no longer allow this on my courses, but everyone has to evaluate the risks themselves.
 
I would be curious if the mag pin played any part in the destruction of the mag. I remember debating pinning mags in Ottawa in 91 and we were telling the government that drilling holes in mags may make them unsafe in this type of situation.
 
steveb67 said:
My norc lower and DPMS upper, loves Norc ammo. Ive burned through three crates (1800 rounds) with no issues less than 2 years old. Sounds like an upper issue. Not an ammo issue.
Click to expand...

Or you were lucky. Apparently you just don't want to admit that there is a higher rate of QC issues with the Norinco 5.56. I have two crates and it definitely doesn't give me a lot of confidence reading the surge in stories.
 
Ol' Smokey said:
Can you point to info on catastrophic failures like this with US manufactured ammo?

I'm sure it has happened, but my Google fu must be weak. I can't find any more than a handful of accounts of such catastrophic failures with factory ammo, and most seem to be the result of squib loads that preceded the firing of a normal cartridge.

I'm genuinely interested in knowing how common such things are.
Click to expand...

This, just recently, is only one example of many like this. http://www.m4carbine.net/showthread.php?146480-M4-Blew-Up

No ammo mfg is exempt from making faulty ammo. It's not common at all, I don't know where you're getting this from... but with the insanely high amount of ammo shot through AR's in the U.S., it's not surprising to see a few in a year.

Also, the OP's failue isn't catastrophic in the least compared to others with american ammo.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom