Military Wiki
300px-PEO M249 Para ACOG.jpg

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 Belgian 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 US Armed Forces. The weapon 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 M249 provides infantry squads with the heavy volume of fire of a machine gun combined with accuracy and portability approaching that of a rifle.

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 where the magazine spring has difficulty feeding rounds quickly enough to match the SAW's high cyclic rate.

M249's have seen action in every major conflict involving the United States since the US invasion of Panama in 1989. Soldiers are generally satisfied with the weapon's performance, though there have been reports of clogging with dirt and sand.


A U.S. Marine fires a first-generation M249 SAW from its bipod during the Persian Gulf War in Feb. 1991.

In 1965, the US Army and US Marine Corps' primary machine guns were the M2 Browning and M60. The M2 was a large-caliber heavy machine gun, usually mounted on vehicles or in fixed emplacements. The M60 was a more mobile medium machine gun intended to be carried with the troops to provide heavy automatic fire. Both were very heavy weapons and usually required a crew of at least two to operate efficiently. The M1918 Browning Automatic Rifle, the Army's main individual machine gun since its introduction in WWI, was phased out in 1957 with the introduction of the M14 Rifle, which had a fully automatic mode. "Designated Riflemen" in every squad were ordered to use their weapons on the full-auto setting, while other troops were required to use their rifle's semi-automatic mode on most occasions to increase accuracy and conserve ammunition. Because the M14 and M16 rifles had not been designed with sustained automatic fire in mind, they often overheated or jammed. The 30-round and 20-round magazines of these weapons also limited their sustained automatic effectiveness when compared to belt-fed weapons.

The Army decided that an individual machine gun, lighter than the M60, but with more firepower than the M16, would be advantageous; troops would no longer have to rely on rifles for automatic fire. Though the 1960s, the introduction of a machine gun into the infantry squad was examined.

In 1968, the Army Small Arms Program developed plans for a new 5.56mm caliber LMG, though no funds were allocated (5.56mm ammunition was viewed as underpowered by many in the armed forces). Studies of improved 5.56mm ammunition, with better performance characteristics, began. The earliest reference to studies of other caliber cartridges for the LMG did not appear until 1969. In July 1970, the Army finally approved development of an LMG, with no caliber specified. At this time, the nomenclature "Squad Automatic Weapon" (SAW) was introduced.

When the time came for developmental and operational testing of the SAW candidates, three 5.56mm candidate weapons were included: the M16 HBAR, a heavy-barrel variant of the M16 designed for prolonged firing; the FN Minimi; and the HK 23A1. The initial round of tests ended in Dec. 1974. In Feb. 1976, the Minimi and Rodman XM235 SAW were selected for further development. In June, it was requested that the SAW specifications document to be revised to emphasize standard 5.56mm ammunition.

In May 1980, the FN XM249 was selected as the best choice for future development on the grounds of performance and cost. The official adoption took place on 1 Feb. 1982.

The new gun entered US Army service as the M249 squad automatic weapon in 1984, and was adopted by the US Marine Corps a year later. The US production model has a different butt from that of the regular Minimi. It is manufactured in the FN factory in Columbia, South Carolina.

Design details

A US Marine firing a M249 from a M122A1 tripod at a training range.

The M249 is a belt-fed light machine gun. It fires the 5.56x45mm NATO cartridge, usually a combination of one M856 tracer and four M855 ball cartridges fed from M27 linked belts. Belts are typically held in a hard plastic or soft canvas box attached to the underside of the weapon.

It fires from an open bolt and is gas-operated. When the trigger is pulled, the bolt and carrier move forward under the power of the recoil spring. A cartridge is stripped from the belt, chambered, and discharged, sending a bullet down the bore. Expanding propellant gases are diverted through a hole in the barrel into a chamber. This pressure moves a piston providing the energy to extract and eject the spend casing as well as advance the belt and compress the recoil spring, thus preparing for subsequent shots.

The barrel has a rifling twist rate of one turn in 180mm. The M249 provides accuracy approaching that of a rifle, combined with the sustained volume of fire of a machine gun. Its original gas regulator offered two different gas port sizes, allowing cyclic rates of fire of 725 rpm or 1000 rpm. The latter setting was intended for adverse conditions such as an excessively dirty firearm or cold weather.


M249 PIP

The product improvement program kit replaced the original steel tubular stock with a plastic stock based on the shape of the heavier M240 machine gun. The change in stocks allowed for the addition of a hydraulic buffer system to reduce recoil. A handguard was added above the barrel to prevent burns, and the formerly fixed carrying handle was swapped for a folding one. Over the years, additional modifications have been introduced as part of the Soldier Enhancement Program and Rapid Fielding Initiative. These include an improved bipod, 100 and 200 round fabric "soft pack" magazines, and Picatinny rails for the feed tray cover and forearm so that optics and other accessories may be added.

M249 Para

A ranger providing overwatch.

The M249 Para is a compact version of the gun with a shorter barrel and sliding aluminum buttstock, so-called because of its intended use by airborne troops. It is much shorter and considerably lighter than the regular M249. The Army's Rapid Fielding Initiative is in the process of replacing the original collapsible buttstock with an adjustable model based loosely on the design of the M4 carbine buttstock.

M249 Special Purpose Weapon

This lightweight and shorter version of the M249 is designed to meet USSOCOM special operations forces requirements. The carrying handle, magazine insertion well, and vehicle mounted lug have all been removed to reduce weight. As a result, the SPW cannot be mounted in vehicles or use M16 magazines. Picatinny rails were added to the feed cover and forearm for mounting optics, lasers, vertical foregrips, and other M4 SOPMOD kit accessories.

The different rounds that can be loaded into the M249.

This is a variant of the special purpose weapon adopted by USSOCOM. The program, which led to both the Mk 46 and Mk 48, was headed by the US Naval Special Warfare Command. Like the SPW, the carrying handle, magazine insertion well, and vehicle mounting lugs have been removed to save weight. However, the Mk 46 retains the standard M249 plastic buttstock instead of the collapsible buttstock used on the SPW.

Mk 48

This is a 7.62x51mm NATO version of the Mk 46, 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.

Operational history

The M249 LMG entered service in 1984 as the M249 SAW. Initial reactions to the gun were mixed: it fulfilled the LMG role well when fired from the ground, but was not as effective when fired from the shoulder or hip. It was praised for its extreme durability and massive firepower, though a number of areas for improvement were highlighted.

The M249 was not used heavily before the 1991 Gulf War, though it has been used in every major US conflict since. Surplus weapons were donated to Bolivia, Columbia, and Tunisia.

Persian Gulf War

929 M249s were issued to personnel from the US Army and USMC during the Persian Gulf War. Although the exposure to combat was scarce, M249 gunners who were involved in fighting mainly used their weapons to provide cover fire for friendly maneuvering troops from fixed positions, rather than maneuvering with them. There were many complaints about the weapon clogging with sand after prolonged use.


The standard SAW in Afghanistan is the M249 with PIP kit, which serves alongside its heavier counterpart, the M240. Almost every squad deployed its two M249s. Most M249s were given a collapsible buttstock immediately prior to the invasion to reduce the length and make the weapon more practical for parachuting and close-quarters.

A report entitled Lessons Learned in Afghanistan was released by Lieutenant Colonel Charlie Dean and SFC Sam Newland of the US Army Natick Soldier Center in 2002. They found that 54% of SAW gunners had problems maintaining their weapons, and 30% reported the gun rusted easily. Soldiers reported ammunition boxes rattling and falling off. 80% of soldiers surveyed were pleased with the weapon's accuracy and lethality, yet only 64% claimed they were "confident in their weapon". Weapons clogging up with sand in the desert seems to be the main complaint.

This page uses Creative Commons Licensed content from Wikipedia (view authors).