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. Its a long shot if LSAT would make the cut with the troops, but at least the army is trying.