Comments on: AR-15 Kaboom — “The Worst … I Have Ever Seen”

By: Bruce

Bruce — Tue, 07 Feb 2017 22:40:40 +0000

Over-length cases can cause nasty things to happen, even with correct powder loads.

TRIM YOUR BRASS!

The scrap metal in question had more than an un-trimmed case, I suspect.

25 grains of Bullseye? That would be like stuffing a pellet of C-4 into the .223 case.

Bargain “Bulk” powder mis-labeled?

I doubt that there would be residual powder left in a thrower when changing from pistol loads (3 to 7 grains, for example) and twenty-plus grains of a proper rifle propellant. How many shuttles of the thrower hande take place whilst calibrating the charge on a set of scales?

What all this does indicate, is that when an “AR” blows, it is probably a lot less of a hazard to the firer than a typical bolt-action.

Firstly, because the action is essentially only open at the bottom, initial “gas leaks” go downwards, typically via the cartridge stack in the magazine.

Secondly, because the upper and lower are, (or should be) made from an Aluminium alloy (7075 or similar) forging, if a “Ka-BOOM!” occurs, it TEARS rather than shatters.

SCUBA divers will be aware of the horror stories about the old steel air tanks in wide use before aluminium became the norm. When a steel tank failed under pressure, it fragmented like a giant hand-grenade. The aluminium tanks flex and “bulge” before tearing open, usually in a straight line, along the length of the tank body. This is because, like a gigantic cartridge case, (or beer can), SCUBA tanks are produced by deep-drawing, and thus the “grain-structure” aligns with the direction of the drawing process.

This is why hydrostatic testing is done with the SCUBA tank submerged in a very large tub of water. The water also helps keep the metal cool as the compressed air is pumped in.

By: Randy Peters

Randy Peters — Mon, 06 Feb 2017 22:08:10 +0000

Root Cause Investigation will require full failure analysis of components and residue.
Try contacting this people http://www.reliability.com/index.html
They may create a training file after investigation.

By: Richard

Richard — Sun, 05 Feb 2017 19:37:50 +0000

Like Florian says, need to look at the ammunition. Also, how many shots were fired before this event.

This highlights the need for education in reloading before people start. The Internet is only a starting place and Clubs and Associations are there to help.

And if you do not know what you are doing – useful factory ammo.

By: germanlongbow

germanlongbow — Sun, 05 Feb 2017 16:44:39 +0000

I had same experience in 2000 with a Armalite. Winchester 748 (24) grains SMK 70gr Winchester Brass and Primer. Had shot this load over 500 times without issue. Last shot boom, blew out and into pieces magazine, broke bolt into two pieces, swelled bottom receiver and separated action into three pieces. Winchester requested ammo and tested themselves. Stated all were within spec then wrote me a check that covered complete rifle. I had it looked by rifle company, stated not their problem since I was using my own reloads. Never gave a reason to why it happened. Trip to ER to get some metal shavings out of my chin and cheek.

By: Mike Bykowski

Mike Bykowski — Sun, 05 Feb 2017 16:08:51 +0000

Obviously a high pressure event. My guess is two bullets loaded in a single round in combination with a material problem. I have seen many over pressure failures in my 35+ years of working with AR-15’s I have never before seen a hoop stress failure of a barrel extension. Normally the bolt lugs sheer leaving the extension intact. There may be evidence of the double bullet theory in the throat of the barrel. Testing of the material property’s of the barrel extension would be more difficult and expensive. As in the other failures that I have seen – the shooter was not seriously hurt. We will never know what happened for sure but this is my guess. Thanks for listening. mike Bykowski P.E.

By: Mike

Mike — Sun, 05 Feb 2017 15:44:27 +0000

I have had one go kaboom also, but we found the big was machined wrong and allowed the firing pin to strike the primer out of battery before the bolt lugs were engaged. This was an A-10 and 243 loaded normal. The magazine opened up and upper was damaged the brass case was in pieces. Now I inspect all bcg to insure the firing pin does not follow the bolt as the bolt I extended to the open position. The defective bcg allowed the firing pin to follow and fall out of sight verses being held by a shoulder in the carrier.

By: guy4064

guy4064 — Sun, 05 Feb 2017 14:23:44 +0000

Ya the only way your going to do that is a full case of pistol powder shot by someone that shouldnt been reloading in the first place.

By: Captain Dave Funk

Captain Dave Funk — Sun, 05 Feb 2017 14:13:04 +0000

At my second ever NRA High Power match, the shooter next to me, on the right end of the firing line, had his M1 rifle explod on the first shot. It was in Fairbault, MN in the early 1990’s time frame. Turns out he had made up his first ever reloads and he had WW231 in those 30/06 cases. The gun exploded forward and to the right of the shooter, as designed. Had he been in the middle of the line, we could have had more people injured than just the shooter.

By: Florian

Florian — Sun, 05 Feb 2017 13:53:09 +0000

Hi,

I remember the May 10th kaboom exp(l)osed on http://bulletin.accurateshooter.com/2014/05/ammo-failure-detonation-in-3-gun-match-watch-and-wince which is probably the same reason as the one today.

At the time I gave Paul my answer to explaine the kaboom, but it was not published.

Please find the PDF in english on : http://www.simplyright.ch/accurateshooter/pdf/Kaboom_20140510_ENGLISH.pdf

Best regards from Switzerland !

Florian