El Paso Rifle/ Ammunition Failure 31 March 2011

General Firearms Reloading & Ammunition
1

Searched this forum to see if it was previously posted and searching on El Paso Rifle and ammunition failure didn’t get a hit. If it was previously posted, my bad.

Received a PDF file with the 1st slide containing the following, is this true?

El Paso Rifle/ Ammunition Failure31 March 2011
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During a recent Firearms Instructor Development Course there was an ammunition malfunction. This malfunction resulted in the damage of an Officer’s personally owned M4. The results of our investigation showed this was caused by a telescoping round. This occurs when the actual bullet is not crimped properly to the casing and when it is fed from the magazine into the bolt assembly it telescopes backwards into the casing, causing a drastic increase in pressure. As a result, and out of an abundance of caution, the Training Academy has recalled all practice ammo and encourages Officers to regularly inspect the ammunition in the duty magazines. If you have questions please contact Range Master, Officer David Thompson.

Last Page:
Conclusion
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“Most catastrophic weapon issue I have ever seen in over 30 years of shooting the platform.” –Paul Howe

Edit: if interested, I will email you the PDF file (22 pages)

2

The incident did happen during a training course in which the officer was shooting a string of fire and fired two to three rounds prior to the catastrophic failure. There were also several rounds found on the range during that class that had the bullet pushed back into the case. Based on this, the ammunition that was involved and the rifle were examined at the department and then sent to Remington for more study. Remington has since replaced the officer’s rifle and inspected over 1000 cases of ammunition in an attempt to discover any issues with the rounds. So far, the ammunition has passed Remington’s inspections and the department is still using the rounds, but only for practice…

3

This was posted in another thread.

The bullet being pushed back into the case will not cause a kaboom. What will cause a ka-boom is the bullet sliding forward when chambered and jamming against the rifling

4

If I knew how to save pictures from a PDF file, I would post the pictures of the weapon.

5

Regardless… the guy should have STOPPED if he saw bullet set back happening.

6

In all seriousness, how would he notice this in real time? From I read, it was post-forensics by Remington and/or the dept that deduced this, and even then, I’d love to know how they arrive at that conclusion. just becasue they see some other rounds laying around that have setback?

It could be many things. one of which is a bullet setback case, probably accompanied by a case that wasn’t fully charged. A perfect storm scenario that results in catastrophic pressure (not just elevated, but catastrophic).

How someone who’s lined up behind the optic, concentrating on the red dot or sight post, or cross hairs, or whatever, and aligning them with the target, and concentrating on trigger manipulation is supposed to realize my carbine successfully chambered the next round, the bolt is seated and rotated closed, but along the way the bullet pushed about .25" deeper into the case , I have no idea.

7

Finally figured out how to copy slides from a PDF file, reported pictures of the failed weapon:

[http://i933.photobucket.com/albums/ad176/slickville/victim12.jpg[/IMG]"]]([IMG)

[http://i933.photobucket.com/albums/ad176/slickville/victim11.jpg[/IMG]"]]([IMG)

[http://i933.photobucket.com/albums/ad176/slickville/victim10.jpg[/IMG]"]]([IMG)

[http://i933.photobucket.com/albums/ad176/slickville/victim9.jpg[/IMG]"]]([IMG)

[http://i933.photobucket.com/albums/ad176/slickville/victim8.jpg[/IMG]"]]([IMG)

[http://i933.photobucket.com/albums/ad176/slickville/victim7.jpg[/IMG]"]]([IMG)

[http://i933.photobucket.com/albums/ad176/slickville/victim6.jpg[/IMG]"]]([IMG)

[http://i933.photobucket.com/albums/ad176/slickville/victim5.jpg[/IMG]"]]([IMG)

[http://i933.photobucket.com/albums/ad176/slickville/victim4.jpg[/IMG]"]]([IMG)

8

Had too break up into two postings, they are out of sequence from the original PDF file, start at the bottom and view up. For both postings.:

[http://i933.photobucket.com/albums/ad176/slickville/victim3.jpg[/IMG]"]]([IMG)

[http://i933.photobucket.com/albums/ad176/slickville/victim2.jpg[/IMG]"]]([IMG)

[http://i933.photobucket.com/albums/ad176/slickville/victim1.jpg[/IMG]"]]([IMG)

9

I assumed that the shooter noticed this. If not… obviously he would have no idea that it was happening.

10

The broaching operation on the barrel extension can cause repeated setbacks to occur. The manufacturing broach is run fore-to-aft, and can raise knife like burrs that will cut and capture the projectile as it traverses either the right or left feed ramp.
To check for this, especially on heavier projectiles with a longer shallow taper nose profile; FIREARM on SAFE or “sans” firing pin…
[ul]
Using the charging handle, pull back until the bolt stop releases, let the bolt slowly strip a round from the mag, ,[/ul]
[ul]
Apply gentle downward pressure to the bullet nose while allowing it to slowly feed into the feed-ramp, between the locking lug cuts at the feed ramp’s center
[/ul]
[ul]
If/when the bullet becomes impinged between the broach-cut locking lug edges, manipulate the forward assist and observe the bullet, if it further engraves by the lug edges, and can’t escape, use the forward assist (simulating bolt carrier inertia) to see if this will begin to seat the bullet back.
[/ul]
The primary (and recommended preventative measure) is to debur the 4 locking lug groove edges adjacent to the two feed ramps. I use cratex and a dremmel, and it is MUCH easier to do this before assembling the barrel to the upper rcvr.

Typically a cannilure type crimped Mil-Spec round is impervious to this problem for two reasons. 1st the crimp is doing its job, second and more significantly, the more abrubt “stubby” 50-60’ish grain projectiles have a profile which is not “apt” to wedge easily. 80 grainers are MUCH more susceptible, as they nestle well into the groove and become “seized” abruptly, seating back to VERY dangerous depths. I have seen them STOP the action, requiring some effort, (twisting) to dis-lodge.

Non-crimped seamless projectiles (w/o cannilure) are prone to this problem, which is compounded by rough/sharp barrel extension cuts which are not properly deburred before use on a barrel.

11

Well, I’m glad that MistWolf is not the original author of that quote because it’s wrong. In fact, bullets are often seated to a micrometer controlled depth to meet the rifle lead (leed, not lead) by benchrest shooters which has the effect of improving accuracy by pre-engaging the rifling when the cartridge is seated by the bolt. A few thousandths will not lead to appreciable pressure variations–no more than the variation in charge from case to case.

And who the hell uses match ammo for a tactical carbine? Match ammo has a “looser” crimp and should not be used in an M4 anyway.

In fact it is the compression of the charge that leads to higher pressures. When the looser crimp allows a bullet to be seated deeper in to the case (either from recoil or chambering) not only is the chance of a malfunction higher due to a misfeed but the chance of a catastrophic weapon failure as in this example.

Read the SAMMI web site for more info, or the cautions in any reloading manual.

My $0.02

Scott

12

Fogetting all the theories of how it might have happened, I’d love to have an engineer step forward and postuilate based on the condition of the weapon, approximately how much pressure would be needed to generate those effects. Once we know the pressure threshold, then we can theorize as to what happened to generate those required pressures.

Let’s just say I’m skeptical that bullet setback and light neck tension alone could cause this. I could be wrong though…

13

I agree COMPLETELY. I’ve had some impressive “oomphs” without the kind of failure shown here. I forgive the receiver (halves) but the chamber? I’d love to see the metallurgical report. I’ve played with S&W 29 and 629 load using Unique (a powder) and held my breath but that was an impressive failure by any standard.

14

To me the photos indicate a bullet was stuck in the barrel. Then another round was fired and…kaboom! But I’ve been wrong before.

15

You’d have to know what ammo they were using! Bullet set back will dramically increase pressures! For that kind of damage the pressure was most likely 80000 psi plus!:eek:

16

Not true at all. Having the bullet seated too deeply can easily blow a gun up. A friend’s AR did almost exactly the same thing when he had a round of HSM 55gr ball go high order, cause was the bullet being pushed into the case.

17

Interesting.

Just off a quick-look it appears he had a bullet lodged in the bore and followed with another round. Pressures peaked and the gas had to go somewhere, following the only paths it could go – rupturing the case head and flowing under the extractor, and blasting through the carrier key and bulging/splitting the carrier and upper.

Upper failed port side forward then fractured along the charging handle track and base of the Pic rail bevel (no place for the gases to escape on port side of carrier – other gas expelled through the starboard carrier vent holes and down the magazine well.

Would have been epic to see.

The bolt and barrel extension were the heroes here – although they cracked they held together.

This was bad but could have been lots worse.

18

Just off a quick-look it appears he had a bullet lodged in the bore and followed with another round.

This is easy to diagnose since having a squib in the barrel and firing another behind it almost always means a bulge in the barrel.

The loose bullet popping out of the case mouth and being stuck in the rifling normally means (in my direct observation) that the next round cant chamber, although if you had a bullet stuck in the leade and then another round behind with the bullet telescoped into the case you would have a spectacular failure, no doubt.

19

This is easy to diagnose since having a squib in the barrel and firing another behind it almost always means a bulge in the barrel.

Correct. Being a thicker Colt barrel it may not have bulged or been obvious without borescoping.

20

Has nayone published interviews with the shooter to see if he/she sensed the round immediately prior may have been a squib or did it have a normal report/recoil?