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Weapons: Radical New Machine-Gun Design
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July 21, 2009: The U.S. Army has come 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.

So the army called together some of its small arms manufacturers, put AAI Corp in charge, 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 (Lightweight Small Arms Technology). 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 38.3 pounds the M249, and 600 rounds of ammo, weighs (and what a machine-gun armed soldier has to carry)..

So in the last two years, the LSAT was developed, built and tested. Not field tested to the point that it can be issued to the troops, but tested enough that everyone agrees it works. The LSAT actually comes in two versions. One uses ammo using a non-metal, telescoped case, and the other uses caseless ammo. 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 19.9 pounds lighter than the current M249 and its ammo. The new plastic case and the LSAT is 15 pounds less than the M249.

The LSAT will be ready for troop testing in two years. At that point. Eight LSAT machine-guns and 100,000 rounds of the telescoped ammo will be delivered for army troops to actually use. If the LSAT passes this test, a rifle using the same technology can be built, and in five years, the design of both weapons 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. ItÂ’s a long shot if LSAT would make the cut with the troops, but at least the army is trying.


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sinoflex    LSAT Presentation   7/21/2009 7:15:00 AM
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trenchsol       7/21/2009 12:11:56 PM
New ammo will lead to development of new assault rifles, if works. Maybe that was the reason why US Army kept M-16/M-4 for so long.

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doggtag       7/21/2009 2:15:21 PM
The only thing I don't like about it is,
there are just too many people who still think that the 5.56mm ammo family is the end-all, be-all caliber for ARs.
I think it would be a good idea that any future small arms (ARs and SAW-type LMGs) should be easily converted (minimal work) if at some point in the future, a newer caliber is needed
(like in the instance of more adversaries acquiring body armor: the US hasn't had to deal with that yet, but it's stupid to think we never will, unless we always forever more intend to fight in "bully mode" against minimally-equipped adversaries only).
Here's an interesting new design to come along, the Italian Beretta ARX-160.
Seen here,
it's also an article in the June 2009 (page 24) Defense Technology International.
What's interesting is that it's claimed that the 16-inch barrel model, with a 30-rd steel magazine,
is still 7oz ( 0.2kg, or about half a pound) lighter than the FN SCAR with a 13.8-inch barrel.
In the design of the ARX-160, you don't need a completely separate upper receiver and barrel group to change the caliber.
Rather, in this instance, it's done by changing the barrel, bolt head, and lower receiver (optimized magazine well for a given caliber's magazine dimensions),
and it doesn't require any special tools to do it.
Current caliber options listed are Russian 5.45mm, 5.56mm NATO, 6.8mm SPC, and Russian 7.62x39mm (here, the two Russian calibers would need the lower reciever changed, but seeing as the 6.8mm is designed to 5.56mm magazine dimensions, in this case I believe it would only be a barrel change and bolt head).
And I like the fact that it's designed, like some newer ones are doing, to be ambidextrous for either-handed firers
(a quick process to switch from right-hand to left-hand ejection,
and change the charging handle from one side to the other, manually in the field), something the US and many others never take into account.
My biggest concern would be how well-balanced the ARX-160 feels when up-gunning to larger ammo.
Will the new LSAT-based guns suffer from such?
A generally bad idea if the new weapons are too tailored to the 5.56mm ammo, to the point that they become unwieldy using larger, more powerful ammunition when that course of action becomes preferrable.
I would like to think we in the US are smarter than that, but then again, our procurement process track record is not the greatest example for the world to follow.
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Das Kardinal       7/21/2009 10:52:15 PM
The pivot thing sounds a lot like the CTA40's loading mechanism. 
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Das Kardinal       7/21/2009 10:53:31 PM
The pivot thing sounds a lot like the CTA40's loading mechanism. 
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sjdoc    Doesnt caseless ammo...   7/22/2009 4:52:10 AM
...punish the hell out of the firing chamber?  Would the weapons conceived to employ such ammunition be designed so that an armorer could readily replace or re-line the surface likely to be extraordinarily hammered by a light machine gun firing such rounds?
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arodrig6       7/24/2009 7:27:46 PM


...punish the hell out of the firing chamber?  Would the weapons conceived to employ such ammunition be designed so that an armorer could readily replace or re-line the surface likely to be extraordinarily hammered by a light machine gun firing such rounds?

The presentation sinoflex posted addresses some of this. Slide 25 indicates that they are testing various chamber coatings to reduce the punishment in caseless (CL) mode. The CL ammo is slightly smaller than the telescoping rounds, which should help.
However, it also points out that the CL ammo is at Technology Readiness Level (TRL) 4 - while the telescoping rounds are at TRL 5.  TRL 4 means 'validated in laboratory' enviornment, so it is quite a bit behind TRL 5. Often bringing something from TRL 4 to 6 is called 'bridging the valley of death' - this is where the hard work occurs and where many seemingly-good ideas die.
So, both technologies are moving along, but have a way to go, especially CL. 
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CJH    Lightweight Small Arms Technologies program    8/9/2009 12:29:54 PM
American Rifleman has a long history of showcasing the latest developments in military arms and ammunition. What follows is a close look at cutting-edge work that is well underway toward the goal of sharply reducing the infantry soldier?s combat load. It could be the future of U.S. infantry weapons.

By Robert Bruce

<a href="">LSAT- the future of small arms</a>
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