The first video shows an M-4 being subjected to an intensive sustained-firing test. The rifle used is the standard M-4 with a standard barrel. The weapon is secured on a bench and fed one full 30-round magazine after another without rest beyond the time it takes to replace empty magazines with full magazines.I've seen M16s and M4s go red hot during sustained firing at Knob Creek, and I've seen AR barrels twist like pretzels when thrust red hot into cold water, but I've never seen a barrel rupture like the test barrel in the first video.
Watch the video closely. After several magazines, the barrel smolders. Then it becomes red hot. After 1 minute and 20 seconds the barrel begins to droop between magazines — like a piece of warm licorice. Then comes the catastrophic ending, at 1 minute and 51 seconds and after the 535th round, when the barrel ruptures.
It is worth noting that the test simulates conditions that almost no soldier could face. In it, 18 magazines are fed through the rifle in less than two minutes. Soldiers and Marines armed with an M-4 or M-16 (the carbine’s longer-barreled parent) typically carry seven or so magazines.
Not to defend the M4, but I do wonder if it's possible to build anything short of a squad automatic weapon that can stand up to sustained full auto fire. Obviously in the Colt tests the heavy barrel held up better, but it didn't make 1000 rounds either. I would rather see the military closely studying the results from competitions like Dave Lauck's hellish ITRC, where the carbine shooters can expect to run 1000+ rounds through their guns under as close to real world conditions as Dave and his military buddies can tinker together — an event designed to stress the guns to the max. There is a ton to be learned watching guns fail under these "lab" conditions!
As we said when we did the torture test on the Para 1911 a couple of years back, heat is the natural enemy of all metal, and we know how to generate a lot of heat.
12 comments:
I haven't seen a rail-mounted air conditioner, but I am sure LaRue could whip one out
If my internal ballistics info is still good (correct me please if I am wrong), as I recall the "core" temperature of the gunpowder gas column reaches something along the lines of 6,000 degrees F. The edge of the column that touches the barrel (believe it or not it cools down in just tenths of an inch) is around 2,000 degrees F. Not much can stand up to that with no break between.
I wonder why when they created the M4 they decided to go back to the semi/full select fire options of the M16A1 instead of keeping the semi/3 round burst options of the M16A2. Seems to me a rifle that only has a 3 round burst option instead of a full auto option would be more nominally accurate in 3rd burst mode vs full auto mode plus it would waste less ammo and be somewhat less prone to overheating.
As you know, this was why the HK 416 was so good because the added piston ran so much cooler. Still, I have watched a AK 47 clone catch fire on You Tube after a similar rapid fire exercise.
This is why the military will remodel the service rifles to something similar to the HK 416.
Long overdue. I think your right that folks like us don't really need to worry about this on our rifles unless we are heading to the sandbox...
Try that with one of those Bullpup rifles. Love to see the same test done with an SA80 or Aug.
To the Anonymous poster:
The issue M4 uses a 3rd burst trigger group, not full-auto. Only the M4A1 is shipped with a full-auto trigger group.
The test M4 carbine was equipped with a full-auto trigger group to simplify things for the demonstration.
Makes that white-hot-barrel-in-Afghanistan story even less believable.
Is it just me or did the second video seem like it had a slower rate of fire?
From what I've heard, it's not just heat that is causing problems with these guns in theater.
I want one of those engines that they test at 50,000rpms. Just how sad are the writers/editors at The NYT that they either let something like this slip by or, worse, actually don't understand how stupid it really is
The M4A1 was equipped with a full auto trigger group at the request of SOCOM, who pretty much are the only soldiers using it.
Frankly, 3-round burst is a solution in search of a problem. if you need full auto fire at all, it's probably not 3 rounds that you need. If 3 rounds are a viable solution, semiautomatic fire is generally better.
Where full-auto in an assault rifle comes into play are those times where the problem calls for larger dumps -- like "sterilizing" a dark hallway when you don't want to chuck a grenade, doing "in your face" suppression during a peel manuever for a small team to break contact, etc., "short controlled burts" aren't really what's called for.
Add in the fact that the guys who generally carry M4A1s are the same guys who train enough that they can, on demand, deliver short controlled bursts with their trigger finger, and it gets easier to see why SOCOM likes a full auto trigger group, but line grunts get a 3-round burst setting.
Of course, I'm of the opinion that if you absolutely can not stand having your troops carry a full auto rifle, don't half-step it -- give them semi-only trigger groups. It's still pretty easy to waste ammo on BURST, it just means you have to pump your finger more often. So the extra parts don't actually BUY you anything, performance wise, and it's just more stuff to go wrong.
The soldiers in Wahat(?) Afghanistan a couple years ago did pretty much what that test was. They were fighting off an overwhelming sized Taliban group that actually penetrated the FOB's wire. Troops were emptying mags as fast as they could switch them, until the weapon would quit. Then they would grab another and continue. Some dead soldiers were found with nonfunctional M4's and mounds of brass. When the enemy is within a stones throw, fire discipline tends to get lost.
The problems with that three round setting is a triple sear design that gives you three different trigger pulls. Plus, you may get one, two, or three rounds when you select it, depending on which step it stopped on when last fired. Don't think it is well liked by its users.
Many of the stainless steels have very high temperature resistance; they wouldn't be harmed at all by continuing to fire through a barrel that was so hot there was a visible glow in direct sunlight. I'm not aware that high temperature stainless has ever been used for a gun barrel, but it could be. However, it would be useless for a gas-operated full-auto, because the hot barrel would expand significantly more than the gas tube and bend or snap the tube off. A totally free-floating barrel would be essential; that could be combined with a roller-delayed blowback system like the G3 rifle or the HK21 machine gun, or a recoil-operated system, or any of the others that can potentially work with a free-floating barrel. Because the barrel loses heat faster the hotter it is (radiant heat is lost at the fourth power of temperature), it might be possible to construct a gun that could be fired indefinitely, if it can just stand up to the balance-point temperature where it loses heat as fast as the firing adds it.
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