The M240, officially Machine Gun, 7.62mm, M240, is the US military designation for the FN MAG (Mitrailleuse d'Appui Général, meaning General Purpose Machine Gun), a family of belt-fed, gas-operated medium machine guns firing the 7.62×51mm NATO cartridge.
The M240 has been used by the United States Armed Forces since the mid-1980s. It is used extensively by infantry, most often rifle companies; as well as ground vehicles; watercraft; and aircraft. Despite not being the lightest medium machine gun in service, it is highly regarded for reliability, and its standardization among NATO members is also seen as a major advantage.
All variants are fed from disintegrating belts, and are capable of firing most types of 7.62 mm (.308) NATO ammunition. M240 variants can use non-disintegrating belts (following replacement of a few easily swappable parts). There are significant differences in weight and some features among some versions which restrict interchangeability of parts. The M240s used by the US military are currently manufactured by FN Manufacturing, a US-based branch of FN Herstal.
The M240B and M240G (see Variants section) are usually fired from an integrated bipod such as a: vehicular mount, the M192 tripod that is mostly used by the U.S. ARMY, and the M122 tripod (a slightly updated M2 tripod) that is mostly used by the U.S. Marine Corps.
Manufactured by Fabrique Nationale, the FN MAG was chosen by the U.S. military for different roles after large world-wide searches and competitions. It has replaced the M60.
The MAG is a belt-fed, gas-operated, air-cooled, crew-served, fixed headspace weapon. Its versatility is demonstrated by its ability to be mounted on the M122A1 tripod, a bipod, on vehicles, or on aircraft. The M60 is still, in some cases, used by the Navy.
It was first adopted by the U.S. Army in 1977, as a coaxial tank gun, and slowly adopted for more applications in the 1980s and 1990s. The M240 and M240E1 were adopted for use on vehicles. This led to further adoption in more uses, especially for the Army and Marine infantry. While possessing many of the same basic characteristics as its predecessor, the durability of the MAG system results in superior reliability when compared to the M60. The MAG actually has a more complex gas system than the M60, but gives better reliability combined with lower maintenance requirements, though this comes at greater manufacturing cost and weight.
Compared to other machine guns, its rating of 26,000 Mean Rounds Between Failure (MRBF) is quite high for its weight—in the 1970s when it was first adopted it achieved about 7,000 MRBF. It is not as reliable as some very heavy older designs, but it is quite reliable for its mass.
The U.S. Army is currently working on reducing the weight of the M240B variant by between four and seven pounds, in the M240B Weight Reduction Program.
The US adoption of the MAG has its origins in the late 1960s/early 1970s as a project to procure a new coaxially mounted 7.62 mm machine gun for tanks to replace the M73 and M219 machine guns then being used. It would go on to be deployed in this role in the 1980s, but was additionally adopted for infantry and other uses. It was deployed in these new roles in the 1990s and 2000s (decade).
As mentioned, during the 1970s the Army was looking for new 7.62 mm machine guns for vehicle/AFV mounts. The 1950s-era M73 had been rather troubled, and the derivative M73E1/M219 was not much of an improvement. A number of designs of the period from various countries were considered; the final two candidates were the M60E2 and the FN MAG. They underwent comprehensive testing alongside the older M219 for comparison.
Two main criteria analyzed were Mean Rounds Between Stoppages (MRBS, jams that can be cleared within minutes) and Mean Rounds Between Failures (MRBF, such as a part breaking).