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.
Development began with the two types of weight-reducing ammunition, and a light machine gun to serve as a testbed and technology demonstrator. Use of an LMG for this purpose is notable, considering its greater technical complexity than infantry rifles. The use of advanced computer simulations to accelerate development may have mitigated this, and the less significant LMG platform succeeds at being less conspicuous to unwanted media attention. For development, the use of extensive computer simulation and modelling reduces both time and expenditure for prototyping and testing. The program also uses a 'spiral development' approach, whereby the weapon and ammunition is rolled out in stages or 'spirals', each stage producing a new version that is an improvement on those from previous spirals. A competition down-selected the design concepts of various companies to leave an AAI Corporation-led team of companies as the developers of the weapon system. The cohesive team of companies is combined with government support to ensure success. The parallel development of the two ammunition types meant that, if the caseless ammunition effort succeeded, much of the development work gained with the composite cased weapon could be applied to it, and, if it failed, the composite-cased version was likely to succeed on its own.
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.