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I'll take two, plz.

From Jim Dunnigan at Strategy Page (used with permission, all rights reserved by copyright holder).

Ultra-Light Machine-gun Passes Tests
by James Dunnigan
December 11, 2012

The U.S. Army finally got its lightweight 5.56mm machine-gun. The new LSAT (Lightweight Small Arms Technology) machine-gun weighs 4.27 kg (9.4 pounds) compared to 8 kg for the current M249. Moreover, the ammo for the new machine-gun is up to 39 percent lighter as well. Thus the new machine-gun, with 1,000 rounds of ammo, weighs 13.9 kg (30.6 pounds), which is 40 percent less than an M249 with a thousand rounds. Moreover, the new ammo takes up twelve percent less space. Developers are working on caseless 5.56mm ammo that will take up 40 percent less space.

It was six years ago the U.S. Army came up with a radical new machine-gun design, mainly to save weight. The U.S. Army is really making an effort to reduce the load the infantry have to carry into combat. In both Iraq and Afghanistan infantry have been doing most of the fighting, and the troops are using the Internet to hammer the brass and politicians about the excessive loads they have to carry.

In the beginning the army called together some of its small arms manufacturers, gave them some money, and told them to come up with a much lighter 5.56mm light machine-gun. In effect, replace the M249 with the LSAT. “Start from scratch” the weapons wonks were told. The only constant were the caliber of the weapon (5.56mm) and the troop handling of the LSAT should be roughly the same as the M249. The goal was to greatly reduce the 17.41 kg (38.3 pounds) the M249, and 600 rounds of ammo, weighs. This is what a machine-gun armed soldier usually has to carry into combat.

Over the last five years the LSAT was developed, built, and tested. LSAT recently passed its first field tests, which involved having eight prototypes firing 25,000 rounds over three weeks. Now everyone agrees it works. More testing is required to ensure ruggedness and reliability, then, within perhaps two years, it will be issued to the troops.

The LSAT actually comes in two versions. One uses ammo using a non-metal, telescoped case, and the other uses caseless ammo. The telescoped ammo is ready for use now while the caseless stuff is still in development. Both LSAT weapons feature a revolutionary ammo feed that employs a pivot, rather than a bolt, to load the ammo into the chamber. This design propels the case out the front of the weapon. Naturally the caseless ammo has no case to eject. The use of the pivot reduces overheating problems, which are more of a hassle with the plastic case of non-metal telescoped cartridge prototype (which is a straight case, like a pistol, not a bottleneck case more common with high powered rifles). The caseless round is the ideal solution but this design is more difficult to manufacture. Caseless rounds have been developed before but are more expensive and more vulnerable to rough handling. But if the caseless round were used, the LSAT and 600 rounds would be 9 kg (19.9 pounds) lighter than the current M249 and its ammo. The new plastic case and the LSAT is 6.8 kg (15 pounds) less than the M249.

Earlier this year eight LSAT machine-guns and 100,000 rounds of the telescoped ammo were delivered for army troops to actually use and passed field tests. Now a rifle using the same technology can be built and in five years would be ready for production. All this turns on whether or not the LSAT passes muster with the troops and the realities of use in a combat zone. The new machine-gun will be much appreciated by infantry operating in Afghanistan, where the machine-gunner is often lugging his weapon and all that ammo up steep hills.


Interesting, but I'm assuming that since it's a new, plastic cased round, that it's not compatible with other 5.56mm ammo.  Certainly the caseless version could not be used in existing military weapons.  So, if true, why the restriction on bore size?

The rationale behind the M249 was a weapon that provided a machine gun capability at squad level the used the same ammunition as the rest of the squad and could fire it in linked or standard 30 round M4 magazines.  Made sense, and reduced the weight of both the M60 and the 7.62 ammo that was the defacto squad automatic weapon even if it came from a difference paragraph on the TO&E.

Looks to me like we have improved on the weight issue and gone backwards on the ammo compatibity issue unless we intend to replace all rifles with one that fires the new ammo.

I'm sure that the M14 and M60 affecianados will stand up to say that weight doesn't count.  That might be true if I had a platoon of sepoys to hump that stuff for me.
Having now watched the video, I'd say that the developers are a little confused about the effects of the weapons weight on effectiveness.  Recoil is the issue when firing on automatic off hand.  I was personally always biased against firing a weapon from the standing position in large part because the target tended to be armed and was firing back, but its good to have a lighter weapon with less recoil when you need it.

I sure hope that the bullet is enviornmentally friendly.
lvn: I suspect the idea is that they'll transition the assault rifle (M-4 or more likely a new replacement arm?) to use the same ammunition.

Having the same basic ballistics means you don't need to adjust your optics or manual sighting habits, and if you're more concerned with weight reduction to have more rounds for suppression, you'd want to keep the small-bore design.

That's my guess.
 Okaaaay then. You have a new design that won't overheat the bolt and bolt carrier (because there's no bolt), and the new ammo design makes it possible for the soldier to carry 1,000 rounds. I noted that super-skinny barrel on the LSAT. How much fire can it take before it's overheated? Brief doesn't say there's a changeable barrel.

The best SAWs always had some means to deal with barrel heating, but it isn't even mentioned here, but high capacity is sold as an advantage, so one presumes that the gun will handled large-volume fires.

Seems to be a disconnect here. Could it be that the pushers of this new tech don't want to mention the biggest disadvantage of the caseless cartridge? That such ammo doesn't like hot guns? They've sold the advantages of more firepower, but is the tech amenable to even present volumes of fire?
D'you guys ever like *anything*?  8^ D
Some more detail (that answers some of Rivrdog's questions) (from the Wikipedia article, which clearly has contractor/PM input):

The LMGs built made a 44% and 43% reduction of weight (for the cased telescoped and the caseless weapons, respectively). Secondary goals have also been met: the LMG has the potential to improve battlefield effectiveness (due to its simpler and more consistent weapon action, its light weight and low recoil, and its stiffer barrel); its use of recoil compensation (with a long-stroke gas-system, for example) has produced positive feedback regarding controllability; the simpler mechanism of the LMG is both more reliable and easier to maintain; a rounds counter has been integrated to improve maintainability, and the weapon is capable of accepting other electronic devices; improved materials used in the chamber and barrel have reduced heat load on the weapon; and the weapon cost is equivalent to the existing M249. The standard LSAT machine gun weighs 9.4 lb empty, compared to 17.6 lb for a standard SAW. Cased telescoped ammunition weighs 40% less than brass cased ammo, so a 100 round ammunition belt weighs about 2 lb for the LSAT, compared to 3.3 lb for a brass cased belt.[6]
A soldier engages a close range target with the light machine during a military unit assessment at Fort Benning, Ga.

The LMG design is a traditionally laid-out (non-bullpup) machine-gun.[7] It has many of the capabilities of other light machine guns, such as a quick-change barrel, a vented fore-grip, belt-fed ammunition, an ammunition pouch, and a roughly 600 rpm rate of fire. New features include the unique weight, a rounds counter, and a highly stiff and heat resistant barrel achieved with fluting and special materials.[1][8] Possibly the most radical part is its firing action: the weapon uses a swinging chamber. The chamber swings around a longitudinal pivot; it swings from horizontally parallel with the pivot (the firing position), to vertically parallel (the feed position), and back again.[9] A long-stroke gas-piston is used to operate this action. A round is fed into the chamber at the feed position using a rammer, and the new round also serves to push a spent or dud round out of the far end of the chamber. Such rounds are pushed forward, parallel to the barrel, and they slide into a separate mechanism that ejects them out of one side of the gun. The advantages of this whole action include its simplicity, its isolation of the chamber from barrel heat, and its positive control of round movement from extraction to ejection. In the caseless firing version of the weapon, another mechanism is introduced to seal the chamber during firing, accounting for the slightly increased weight of the caseless version.
I'm firmly in the camp of reducing soldier load and view this weapon as a big improvement in that regard.  I am curious about their choice of caliber if they really are moving to a new cartridge for all small arms at the squad level.  Caseless ammo has been the promise since my days as a platoon leader and it's never quite been ready for prime time.  Maybe now it is. Or, maybe in another 20 years.
I get the impression from other reading that Sigi's view is probably correct - they are going to try to make it work here, and then apply it to personal weapons.  The logic being that people with agendas pay less attention to things like LMGs than they do to rifles.   Use the LMG program to push both the weapon *and* the ammunition tech, and when proven, then shift the focus to personal small arms.
I agree...I read somewhere that a bullet of roughly 6.5mm, in the 120-130 grain weight range, is pretty close to the "sweet spot" balance of long range accuracy, terminal ballistics, and ability of the soldier to carry plenty of ammo.  At least as far back as the early 1960s, at least some agencies in the Army were pushing for a 6.5mm...but the powers that be gave us the .223/5.56mm.

Other than the institutional pressure of Big Army not wanting to admit it made a mistake, along with not wanting to spark another round of debate of over rifle cartridges with NATO (after we forced the 7.62 NATO and 5.56 NATO on them), I can't think of a legit reason for not re-looking projectile size, if you're going to a totally imcompatible ammo type anyway.

Bingo. I have read that the railroad guage in the Western world derived in a logical, but somewhat convoluted way from the simple fact that the distance separating the rails equalled the length of the axle of a Roman chariot.  In similar fashion, we appear to have the 5.56 mm and will forever more.
Poodles .... be afraid ... be very afraid
lvn, you wussy Blue Legs are just grousing about the weight. Real men don't complain about such things. Just look at the weight those poor Red Legs have to hump. And the, there's the Navy....

Seriously, there was some hope when the Army was looking at a 6.8mm bullet, but they seemed to be insisting on using the Stoner action and the thing was peening at the back end, so that wouldn't work out. I think the current personal weapon of the Infantryman pretty much requires the 5.56. I know AR-15s have been chambered for stuff as hot as the .50 AE, but no one is going to suck .50 Ae at the same rate as they would 5.56 in combat. The .50 AE chambering is what I call a "play round" because no one is going to use it in combat unless that's all that's available. I have no doubt it's effective, but the converted mags hold only 10 rounds (in a 30 round mag ISTR). You might as well use an SKS. A direct impingment gas system is also a serious weakness in a rifle as well. I have a DR-200 which uses the AK gas system with the Stoner rotary bolt and it works very well. It also has an adjustable gas port which allows for reliable operation. The ROK Army issues it in select fire and I really like the piece. I wish Kimber still sold them so I could buy a couple more. I've been offered $2000 for the thing and won't let it go.

A red flag for the AR-15 action is the fact Stoner designed it to use IMR powders. IMR is OK for a bolt action, but not for an automatic weapon as IMR powders burn far hotter, although much cleaner, than ball powders.

So, let's look at something around 6.5 mm, and a rifle built around a different action that does not use direct impingement. Prolly won't happen though.
Wow, MG Justice, haven't seen him since Monmouth shuttered.

And yeah, I'd love one too please, Santa..

Looks like the technology is about mature on the weapon.  Not so sure about the caseless ammo being ready for use any time soon.

However,  given the realities of Defense funding for the next four years (or more likely all eternity while we pay off the next four years' debt), I predict that this weapon system will never reach regular issue status. 

We will be lucky if we can keep a very small ground force, with whatever already paid for weapons are in our on-hand inventory, and maybe, just maybe, get a few rounds for training use, but a mere fraction of what we use now.
Qm, you are preaching to the choir, here, and I write as a former actual choirboy (First Methodist Church, Coral Gables, FL, Andrea Harris's old church).

On the caseless cartridge:  Isn't that just inviting a nasty fire which you can't put out?  I remember some of those complaints about the Sheridan.

Rivrdog hast recht on the heating. I have just re-read Cryptonomicon and remember how much Sergeant Shaftoe was impressed by the liquid-cooled Vickers, with all of its infrastructure.  As we know, The Armorer has been careful to show us the infrastructure which goes with a Serious Machine Gun.

What do you think will happen if they have to fire it in direct sunlight, or, heaven forbid, the monsoon???
P.s. Oh yeah, Qm, when I was reloading .45ACP for my PD with 231 (ball), I noticed lotsa undead powder particles in there when I went into it to clean it after shooting.

Which reminds  me: I wonder how one would refine the reloading powders so as to dis-inhibit them and extract the pure nitrates?  I figger I am already on 4 or 5 .gov lists, or I would not have written that.  Yes, boys and girls, I do believe that the nasty is coming.

DISCLAIMER!  What I wrote just above is just my own opinion and musing, and should not be interpreted by anybody ( at least, anybody with a working brain)
to be the opinion of, or to be approved by, Our Genial Host.
Referring back to my comment at 8:02; is this really a Serious Machine Gun? I mean, it's nice if it's light enough that one guy can carry it anywhere, and it would be even nicer if it still shoots well when its barrel is red hot.  Yah, I know, short bursts and all that.
 JTG, yes it is a real machine gun, they don't mention it in the video but the LSAT barrel is made from a Cobalt alloy rather than conventional steel for reduced weight and much greater temperature stability.
 It's not intended to fill the role of the Vickers, or M2, etc.  It's more aimed at the Bren niche. JTG.
I may be a bit old fashioned, but when di we start paying suppliers to submit a weapon design?  I would have been hung by my heels and beaten like a pinata for even sugggesting a design enhancement other than the origional requirement specs.
I don't know all the details, but it isn't unusual when we're asking for people to push the envelope into new territory, and one with no obvious commercial value, we've provided seed money to defray the costs of development upfront.  But, like I said, not an area where I have any deep knowledge.
1. The original studies on the 6.5mm as an ideal calebre were done by the Brits in the period 1904-1910. Eventually they led to the post-war EM-2.
2. Caseless ammo was a feature of the H&K G11, whauch had a rotating/oscillating chamber.

 I recall an article in Popular Mechanics, I think, about the H&K Caseless cartridge design. I've never heard anything about it since. I'm guessing there may be a cook off problem with caseless and since barrel heating is a hard physics problem, I'm not sure how the problem would be solved. Nice idea, although I hate the idea we wouldn't be able to get any of that good processed military brass anymore.
Oh, the Bren. Sigh.  How much does a transferrable Bren go for these days, I wonder?
I do so lust after owning one. They are such really nice finely-machined pieces. Not only that, but the magazine is on the top, so you can lie really flat on the ground and still shoot it.
Oh, former-Captain Heinrichs?  I think I am in good company being a 6.8mm/7mm crank, as that seems to be the sweet spot for a smokeless-powder infantry rifle cartridge. The Brits were about to adopt it when  the Great War intervened, and we were thinking  about doing it when General MacArthur pointed out that we had several million rounds of .30-06 lying around.