NEW COMPLETED UPPER,RRA 16INCH BARREL, RRA FLATTOP UPPER, ARMS #40 RRA BOLT AND CARRIER, ALL PARTS NEW.HEADSPACED BY ME AND DOUBLECHECKED BY DEPT GUNSMITH.UPPER WAS BUILT FOR SOMEONE ELSE.TEST FIRING THE RIFLE ALLS WELL, ZERO IT, HAVE PUT 150 ROUNDS DOWN RANGE WHEN EXPLOSION HAPPENS, MAG FLIES OUT THE BOTTOM, SPLIT DOWN THE BACK HALFWAY,MAG CATCH WAS FORCED OUT THE LEFT SIDE, ROUNDS ARE EVERYWHERE,MANAGE TO POP PIVOT PIN AND REAR TAKEDOWN PIN.WHEN I LOOK AT BOLT CARRIER, BOTTOM OF IT HAS SPLIT OFF, LATER I AM ABLE TO DRIVE IT OUT OF UPPER, WHICH HAS BULGED,EXTRACTOR BENT, BOLT SPLIT DOWN MIDDLE,PART OF CASE ON BOLT,REMAINDER IN BARREL WHEN I GET CASE OUT, LOOKS LIKE IT HAS TWO RIMS ON IT. FIND OUT LATER IT WAS REMANUFACTURED AMMO, COULD THIS BE THE REASON, SORRY FOR BEING LONG WINDED BUT HAVE NEVER SEEN THIS BEFORE

your dang CAPS  LOCK  KEY is stuck!

sounds like it fired out of battery.

could be the trigger group in your rifle letting the hammer follow. firing pin stuck in the bolt in the forward position (i've seen people grease the firing pin before). or non-mil-spec primers which would fire as the bolt was closing and the firing pin hit hits the primer.

Classic symptoms of a case head separation.  Standard pressure and a weak case could be the cause as could an overpreasure with a standard case.  No way to tell but either way, it was an ammunition problem.

When the case head fails, high pressure gas can flow back along the extractor causing the carrier to split.  Sometimes the carrier will completly separate causing the upper to split into two pieces.  The remaining ammunition, follower, spring, and floor plate will be blown out the bottom of the mag.  Sometimes the mag well in the lower will be bulged out.

This is a relatively rare occurance.  I recall seeing the problem reported here about once a year.  I believe the army reported one incedent in their initial trials of the M16.

In one report here, the failure was attributed to firing a round that had previously misfead and had gouges in the side of the case.  Another was attributed to using pistol powder in a reload.

I would not use any more of that ammunition.

Several incedents are reported here:
http://www.quarterbore.com/ar15m16/ar15kaboom.html

[img]http://www.quarterbore.com/images/kaboom007.jpg[/img]

Only way you are firing out of battery is a high, soft primer.

From what I have read, that what you have, or a round charged with pistol powder.

I dont think you can double charge a .223 round.

Who reman'd the ammo?  Always the first suspect.

Anything stuck in the barrel?

What ammo?


Not a double load, no room.

Could be a light load - allows the flame front to travel down the whole cartridge - results in a pressure spike

Other considerations based on the ammo involved include a high primer, or the use of a pistol primer. Both can cause an out of battery firing.

Contact the "remanufacturer"..

Meplat-

wrong powder could do it

Sometimes you guys make me wonder...

Simple case seperations occur from too much headspace or heavily used and reloaded cases. While they may give the shooter a bunch of gas and some particles, they do not blow up actions.

If you somehow got a bunch of excess pressure, the case fails when other things give and the mag blows out, the carrier is split, etc. In the aftermath, the case is seperated, but just the seperation does not disassemble the rifle.

The description is of a masssive over pressure. The case head with the belted magnum look is from big pressure. Faster powder or more than should have been in the round, barrel obstruction, long or thick case neck crimping the bullet, etc. Most of these point to the reman ammo, and one points to the shooter.

One notable example ran across these threads, with pictures. Soldier had a round squib on him, leaving a bullet part way down the bore. He performed immediate action, and when he tried to fire, he was trying to put two bullets down the bore with a single charge. Disassembled the rifle... Frank White described a High Master doing a similar thing with similar results. Ouch.

Mr. Billski

The people at Bushmaster seem to disagree with you...

[url=http://www.bushmaster.com/faqs/troubleshootingfaqs.asp#10]Beware the dangers of CHEAP AMMO![/url]
If you shoot enough cheap ammo, it'll happen to you. The rifle is just ticking along, then BAM! The bolt is stuck forward and the magazine blows down out of the rifle. Looking up into the mag. well, you see a crack in the bottom of the bolt carrier. You've just had a case head separation. If you are shooting reloads or surplus ammo, you're out of luck. If you have factory ammo, and the box the shells came in, you can write a letter or call the factory, and they will tell you what to do. We have seen case head failures from overloaded ammo, and from bad brass. There is almost no difference in the result, though. When the case head fails in an AR, the gases flow back into the action. They usually bend or break the extractor, flow along the extractor slot, and crack or break the bottom pad of the bolt carrier. The gases vent out mostly through the mag well, usually wrecking the magazine on the way out. Sometimes the bolt cracks, sometimes it doesn't. In extreme cases, it can crack or break the barrel extension. Many times the bolt catch will break off and the upper receiver will crack by the ejection port. Usually the lower will survive, but sometimes they crack somewhere at the top of the mag well, usually in the front. The front half of the case will remain stuck in the chamber. This is a sure sign of an ammunition failure. If the rifle had failed the bolt lugs would all be sheared off, the stock would be blown off, the gun would probably be blown in half. We've never seen it happen, and we hope we never do.

I never said that you can not get bad ammo. And overpressure ammo will blow up a rifle. I recognize that the AR15 design is sensitive to overpressure and burst cases. If you really want security against that sort of thing, shoot a Rem M700.

Simple separations do occur to AR15's and do not usually wreck rifles. Now if the seperation occurs because the ammo had BIG pressure, yeah the rifle will be wrecked. Under that circumstance, the seperation is a symptom, not the source. The usual way that shooters discover a seperated case is that the next one will not go home because a piece of the last one is in the chamber.

Now, if we want to discuss the consequences of a head split, that will wreck a rifle in the manner described. Head splits are a radial crack through the case head. The source of head splits is ammonia exposure. Some shooters do clean rifles on the same bench where the process reloads...

Try to remember something about Bushmaster. They did not design nor develop this rifle. They build rifles by making parts that look like the government blueprints, right down to the heat treat and finishes. That they do this well is a tribute to their manufacturing capability. But do not mistake them for a comprehensive designer and developer of sophisticated firearms. I seriously doubt that they have deliberately fed normal pressure handloads in cases with stretched webs to rifles until until they failed some cases. I have participated in this process at a comprehensive gun firm with a variety of rifles, and they do not usualy wreck rifles. But expose a batch of cases to ammonia vapor (all copper solvents including Hoppes, urine, household solvents), and you will get head splits. We did those too. They wreck rifles...

If you write me off to arguing semantics, I will only point out that the sources of the failures is different. Splits are due to ammonia. Overpressure can come from several things, some from the operator, some from the ammo builder. And simple seperations usually do nothing. You can make sure that the barrel is not obstructed and that the ammo (and components) are stored clear of ammonia. These will improve your odds immensely.

Billski

First, I value your opinion and aknowledge your experience.

Do you agree with the following?

The carrier and upper receiver parts cannot withstand the pressures generated after a case head separation.  Even with standard or accepted loads and pressures.

Note that the bolt and barrel extension did not fail in the picture.  High pressure gas got back to the carrier and caused them to fail.

Simple splits in the side of the case, near the neck for example, will not cause these catastrophic failures.

I suspect there are many ways to make a case that will fail.  Bad metalurgy, dimensional errors, or manufacturing mistakes for example.

I have noticed my Remington 700 has a hole drilled in the reciever to vent high pressure gas in the event of such a failure.  

Armalite has an even better discription of the failure mode.

[url=http://www.armalite.com/library/techNotes/tnote49.htm]Armalite Technical Note 49, Cartridge Case Failure in the M16 and Similar Rifles[/url]

My thanks to all who replied. After reading the Armalite description of the failure mode, that oldguy suggested, my failure must be due to cartridge case failure.The article stated high pressure gas, bends the front end of the extractor outward, which occurred, the bolt splitting, which occurred, magazine blowing out the bottom, which also happened, upper receiver sides bulging.All and all I am lucky, I had no injuries, I just learned a very valuable lesson to always use quality ammo. Marty

You said it looks like it had 2 rims? If this is the case then the case head most likely separated on extraction leaving the body of the case stuck in the chamber(this is what broken case extraction tools are for) next round loaded up inside of stuck body holding bolt out of battery. Click/BOOM.

Shoot remans if you want but the only detached case heads I've ever seen on BRASS cased ammo was in reman/reloaded ammo. I'll shoot it in a revolver but no auto centerfire rifles.New 5.56 ammo is too cheap to justify reman in my opinion.