The M249 light machine gun (LMG), previously designated the M249 Squad Automatic Weapon (SAW), and formally written as Light Machine Gun, 5.56 mm, M249, is an American version of the FN Minimi, a light machine gun manufactured by the Belgian company FN Herstal (FN). The M249 is manufactured in the United States and is widely used by the U.S. Armed Forces. The gun was introduced in 1984 after being judged the most effective of a number of candidate weapons to address the lack of automatic firepower in small units. The gun provides the heavy volume of fire of a machine gun with accuracy and portability approaching that of a rifle to infantry squads.
The M249 is gas-operated and air-cooled. It has a quick-change barrel, allowing the gunner to rapidly replace an overheated or jammed barrel. A folding bipod is attached near the front of the gun, though a M192 LGM tripod is also available. It can be fed from both linked ammunition and STANAG magazines, like those used in the M16 and M4. This allows the SAW gunner to use rifleman's magazines as an emergency source of ammunition in the event that he runs out of linked rounds. However, this will often cause malfunctions because the magazine spring has difficulty feeding rounds quickly enough to match the SAW's high cyclic rate.
M249s have seen action in every major conflict involving the United States since the 1991 Gulf War. Soldiers are generally satisfied with the weapon's performance, though there have been many reports of clogging with dirt and sand. Due to the weight and age of the weapon, the U.S. Marine Corps (USMC) is considering designs for an infantry automatic rifle, which is planned to complement and partially replace the M249 in their service.
The Mk 48 Mod 0 is a 7.62x51mm NATO version of the M249, used by USSOCOM, when a heavier cartridge is required. It is officially classified as an LWMG (Light Weight Machine Gun) and was developed as a replacement for the Mk 43 Mod 0/1. The M60 based machine guns are a great deal more portable than the heavier M240 based designs used elsewhere in the US military in the infantry medium machine gun role. However the M60 based designs have a long history of insufficient reliability. Trials conducted through the mid-1990s led the US Army to replace its M60 with M240B GPMGs. The M240B however, weighs in at ~27.5 lbs and is about 49' long with the standard barrel. NAVSPECWAR was reluctant to give up the increased portability of the M60 (~22.5 lbs, 37.7' OAL with the shortest 'Assault Barrel') designs in spite of the M240's increased reliability. A request was put in for a new machine gun in 2001, and FN responded with a scaled up version of the M249 weighing in at ~18.5lbs with an OAL of ~39.5'. The new design achieved much better reliability than the M60-based weapons while bettering its light weight and maintaining the same manual of arms as the already in-use M249. USSOCOM was slated to begin receiving deliveries of the new gun in August of 2003.