Lightweight Medium Machine Gun

The Lightweight Medium Machine Gun (LWMMG) is a prototype machine gun being developed by General Dynamics. It is designed to fill the gap between 7.62 mm and .50 BMG machine guns. The weapon uses the .338 Norma Magnum round, giving it greater lethality and double the range of the 7.62 NATO round. The LWMMG has a rate of fire of 500 rounds per minute, an effective range of 1,700 meters (1,860 yards), and a maximum range of 5,642 meters (6,170 yards). It weighs 24 pounds, making it only slightly heavier than the M240L. It is equipped with a quick-change barrel, quad picatinny rails, collapsable stock, and can be used by dismounted troops or mounted on a platform. The gun was first unveiled on May 15, 2012 at the Joint Armaments Conference in Seattle, Washington.

In September 2013, General Dynamics displayed the LWMMG at Modern Day Marine 2013. It was pitched as being a bridge between 7.62 NATO and .50 BMG machine guns. While the M240 has an effective range of 1,100 m, the LWMMG fires a 300 gr .338 bullet that can provide effective and accurate fire out to 1,700 m. General Dynamics officials say their machine gun is not meant to be a replacement for the M240, but to give the ability to put effective fire on targets at extended ranges. 100 rounds of 7.62 NATO weighs 7 lb, while a 100 round box of .338 Norma Magnum weighs 9 lb. The LWMMG can be mounted on an M240 mount and costs about the same. While the company is satisfied with the shorter .338NM cartridge's performance, the gun could easily be converted to .338 Lapua Magnum. The gun's short recoil operating system causes the barrel to reciprocate, similar to the M2 machine gun. This combined with a gas system to minimize recoil balances positive and negative recoil forces, allowing a gunner to fire a round with significantly greater energy, but with the recoil profile similar to a 7.62 mm round from an M240.