November 28, 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.