FAL Explosion

Amazing that Wilson Arms made an aluminum FAL receiver. Equally amazing that DSA made an aluminum FAL receiver.

Amazing because it shows the lack of metallurgical engineering knowledge in the firearms industry. Of course aluminum is going to fail. It has a finite fatigue life. This is very basic stuff.

Now, 4140, that is an excellent receiver steel.

Yeah, but DSA did it for testing purposes, having only made 6 and testing 3 of them. What was amazing was that Williams made them and then sold them and people bought them and made FAL's out of them.

Though, I have heard some good things about the pistol-caliber FAL's made on Williams receivers.

The problem isn't that they are aluminum but that they were designed to be steel. The locking shoulder being embedded in the aluminum means the aluminum is taking the stress. If the bolt locked in the barrel, the receiver would not matter.

Ash

Small correction - Williams, not Wilson, made aluminum upper receivers (aka Alumabombs). I've no personal experience with them but they seem to work quite well for handgun-caliber conversions of the FAL.

Slightly OT - aluminum lower receivers are still made and, as a previous poster mentioned, are not subject to the pressures of a round going off.

Seems to me that Our Tam had a Williams FAL receiver she built up into a .223 FAL. That was, in my opinion, the only safe way to utilize an aluminum FAL receiver. She has since sold the rifle.

Regards,
Rabbit.

Amazing that Wilson Arms made an aluminum FAL receiver. Equally amazing that DSA made an aluminum FAL receiver.

Amazing because it shows the lack of metallurgical engineering knowledge in the firearms industry. Of course aluminum is going to fail. It has a finite fatigue life. This is very basic stuff.

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If that's true, then what's *really* amazing that the U.S. Military, as well as many other militaries in the world, lack this very basic knowledge - they are so dumb they make M16s and M4s out of aluminum. Steel also has a finite fatigue life. It's much greater than aluminum, but it's most certainly still finite.

If that's true, then what's *really* amazing that the U.S. Military, as well as many other militaries in the world, lack this very basic knowledge - they are so dumb they make M16s and M4s out of aluminum.

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Are you aware how those rifles operate?

Rec.'s on AR's are non load bearing, whereas teh FAL's is.

Steel also has a finite fatigue life. It's much greater than aluminum, but it's most certainly still finite.

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As well as not understanding what is, and what is not a load bearing structure, I guess you are also unfamiliar with the Sn curve for steel?

Where did this event transpire?

I have a Williams Aluminum receiver with over 17,000 rounds through it. DSA blew theirs up with proof rounds. While there no doubt aluminum was probably not an appropriate choice for the FAL receiver, if you stick to NATO pressures you probably won't have any issues. Those who read the FAL files when the Williams receiver came out will recall there was numerous torture tests with no kB, and DSA certainly had a vested interest in seeing williams go under - to the point they paid a guy to who worked for Williams to give them info on the company.

In this case, the receiver appears to be steel. And in the case of DSA, you'll notice that they did not subject their own steel receiver to the same test that they applied to the Williams.

The fact of the matter is you can blow up and rifle or other firearm with a hot or improper load. If you get an inclusion in the steel, it can kB with normal ammo. kBs are in fact seen in an firearm you can name, even with normal ammo. Mechanical things fail.

Here's a nice M1A kB:

http://www.thegunzone.com/m1akb.html

Amazing because it shows the lack of metallurgical engineering knowledge in the firearms industry. Of course aluminum is going to fail. It has a finite fatigue life. This is very basic stuff.

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Slamfire1, you are aware that a number of military rifles use aluminum for major portions of their construction? M-16, FNC, the new Bushmaster ACR, FN SCAR, XCR, SIG 556 to name a few? The M16 has been aluminum since day one, and is the longest serving US military rifle.

BTW, aluminum has been used in handgun frames for at least 50 years, including such classics as the P38, Beretta 92, SIG P22x, etc.

It's all about material matched to application.

Fatigue-wise, a multitude of polymers beat steels in terms of lifespan. Notice the frame lifespan of polymer pistols vs steel one, for example. And not all alloys are equal. 7071-T6 is not the same 1199-0

IIRC 4140 has a tensile strength of around 650 MPa. Aluminum alloys like weldalite are over 700. You need to be at least as specific when talking about aluminum alloys as you are about steels. FAL receivers have been made from several steels, including (but not exclusively) 4140. M14 receivers (the FAL US competition) used 8620, IIRC.

Heat treat is also a factor. 4140 annealed won't have the same properties as the same allow at Rc 40.

It's not as simple as 'steel better than aluminum', or any other particular material.

The accident happened at
Mayflower Shooting Range
Mayflower, AR

The rifle that KB'd wasn't built on a DPMS reciever. It was built on an IMBEL receiver. The other rifle that he had was built on a DPMS receiver. He said that he was confident that he could get the rifle back into service, but that he would never sell it to anybody.


That guy is at that range frequently. He always has a freakin' ton of ammo too.

I think that your initial conclusion is correct. It was an out of battery discharge.


BTW, I did not intend for my earlier post to read like a rebuke. But it sure came across like one. Sorry.

Slamfire1, you are aware that a number of military rifles use aluminum for major portions of their construction? M-16, FNC, the new Bushmaster ACR, FN SCAR, XCR, SIG 556 to name a few? The M16 has been aluminum since day one, and is the longest serving US military rifle.

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While that's quite true, the big difference between the FAL and the M16/AR15 design, for example, is how they use aluminum or steel in their construction. The FAL employs a rear-locking receiver that subjects the receiver itself to the stress of keeping the bolt closed during firing. Contrast that with the M16/AR15 that employs a steel barrel extension into which the bolt locks and keeps the bolt closed during firing. The M16/AR15 aluminum receiver serves the function of keeping the parts together--it is not a stressed component.

Slamfire1 is correct; perhaps he should have added that steel has a fatigue limit. Keep stress below this limit, and the steel piece being stressed can endure an infinite number of stress cycles. So, if you keep your FAL receiver beneath the fatigue limit (i.e., shoot loads within SAAMI pressure limits), theoretically you can shoot the gun an infinite number of times without the receiver blowing apart. That's not the case with an aluminum FAL receiver such as the Williams. Aluminum has no fatigue limit. In other words, it doesn't matter how little stress you put on the part, it will eventually fail. Now, if you're talking .22LR pressures (but still using a rear-locking action, not blowback), your aluminum FAL receiver might last a million or a billino rounds. However, as some on the FAL Files discovered (DABTL, FWRA), at .308 pressures the receivers lasted only dozens of rounds before locking shoulders fell out.

Keep stress below this limit, and the steel piece being stressed can endure an infinite number of stress cycles. So, if you keep your FAL receiver beneath the fatigue limit (i.e., shoot loads within SAAMI pressure limits), theoretically you can shoot the gun an infinite number of times without the receiver blowing apart. That's not the case with an aluminum FAL receiver such as the Williams. Aluminum has no fatigue limit.

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Exactly. I reverse engineered the M1a bolt, and the lugs are sized for an infinite loading at SAAMI pressures.

I have not performed the calculations for an aluminum FAL receiver, but it would be interesting to calculate the fatique limit on a 3/8" piece of Aluminum (crossection SWAG) subjected to a 6800 pound load.

An aluminum FAL receiver is going to fail. There are no if's, and's or buts about it. And one fun thing about aluminum, if you get a warning (a visible crack) you are lucky. The stuff fails lots of times without any visible indications.

And to continue flogging a dead horse, lets say the calculated average stress life of an Aluminum FAL receiver is 35,000 rounds. This is a total guess, probably high. I am certain that a 4140 FAL has an indefinite life with SAAMI spec ammo.

So someone come to you with a FAL says I have put 17,000 rounds through my FAL and wants to sell it to you.

If it is a Steel receiver you might think, “maybe needs a new barrel, total new set of springs, maybe a firing pin”, and offer $$$.

If it was an Aluminum receiver, what sort of offer would you make?

Did the little white boxes look like this?




If so, then there is greater than a 100% chance they were handloads. Sounds like he overloaded one of them Not easy to do with a FAL. It was definatly NOT the fault of the gun.

Those who read the FAL files when the Williams receiver came out will recall there was numerous torture tests with no kB,

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Williams swore up and done that he had had testing done. These were bald faced lies.

NO there were never any torture test except the one that Mark Powell, FWRA, did. The very next Williams he got from them KBed on him. One guy made a dealer sample machine gun, yes it was legal, and it failed after 1000 rounds. And this was AFTER Deweight Williams told him that it would not fail. DABTL had a locking shoulder fall out of his. There were many reports of loose locking shoulders. I put about 700 rounds through mine and never had a problem. But after they started to fail I took it off and put on a Entreprise receiver.

If the POS Williams receiver is such a good receiver, then why did he quit making them? Because he knew about the flaws and was running scared.

DSA did EXACTLY the right thing. They sent it to a testing lab. Before you start making judgements, you should read the test the did on their own receiver.

Williams receivers are dangerous and it is just a matter of time till yours fails. Hope you don't get hurt. Have you checked the headspace lately. The always KB at the locking should hole.

I am convenced that this guy had an overcharge problem. OR it is possible that he set the head sapce wrong.

"I am convenced that this guy had an overcharge problem. OR it is possible that he set the head sapce wrong. "

How did you come to that conclusion?

you'll notice that they did not subject their own steel receiver to the same test that they applied to the Williams.

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Close but no cigar

http://www.dsarms.com/pressure_test.asp

Using proof rounds is common practice. Twice the load. See if it will blow up.

And no DSA did not have a vested interest in seeing a Williams blow up. They had an aluminum lower that people wanted to buy to go with the Williams. So why would they have an interest in seeing the receiver blow up? They wanted to see if the receiver would blow up for liability purposes.

None of the 'Smiths on the Files will touch a Williams.

You need to go to the Files and do a search for Williams. Get a beer and set back and read. You might learn something. I lived this fiasco.

I've always wondered how countries that make terrible military ammunition would be effected if they had to use that stuff in a war...

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Countries that make ammo of that quality generally consider their troops to be "disposable" anyway.

If the rec. stil looks good, you can have it magnafluxed locally, pretty much anywhere that heads, cranks, etc, get machined, like an automotive performance shop.