LSAT Light Machine Gun

The LSAT light machine gun, of the LSAT (Lightweight Small Arms Technologies) program, is a developmental light machine gun. The program was initiated in 2004, when the Joint Service Small Arms Program (JSSAP) challenged the American defence industry to develop lighter small arms and ammunition. The LMG provides a major reduction in weight over legacy weapons, as well as improvements in other areas, such as controllability and reliability. As of 2008, it has two configurations, one that fires polymer-cased ammunition, and one that fires caseless ammunition. After further research and development into both technologies and the platforms that fire them, one of the two variants shall be chosen for production.

The LSAT light machine gun 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 LMG design is a traditionally (non-bullpup) laid-out machine-gun. 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. 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. 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 (which is why the caseless weapon is roughly 1% heavier).

LSAT light machine gun
Type	Light machine gun
Place of origin	United States Germany
Production history
Designer	AAI Corporation
Designed	2003 onwards
Manufacturer	TBD
Unit cost	≤US$3600
Produced	Earliest: 2010
Variants	Polymer-cased ammunition firing variant Caseless ammunition firing variant
Specifications
Weight	9.8 lb (4.45 kg) empty (polymer-cased variant) 9.9 lb (4.5 kg) empty (caseless variant)
Length	36.1" (917 mm) (stock retracted)
Barrel length	16.5" (418 mm)
Cartridge	LSAT polymer-cased ammunition LSAT caseless ammunition
Caliber	5.56 mm (At present)
Action	Gas-piston; push-through feed-and-ejection; open, swinging chamber
Rate of fire	≈650 rounds/min
Muzzle velocity	920 meters/sec
Effective range	≈1000 m
Feed system	100 (polymer-cased) or 150 (caseless) round soft pouches of full-loop-polymer linked, disintegrating belts
Sights	optical, involving advanced tracking and acquisition[3]