The M249 SAW (Squad Automatic Weapon), formally the Light Machine Gun, 5.56 mm, M249, is the United States Armed Forces adaptation of the Belgian FN Minimi, a light machine gun manufactured by FN Herstal (FN).

The M249 SAW is manufactured in the United States by the subsidiary FN Manufacturing LLC, a company in Columbia, South Carolina (FN America), and is widely used in the U.S. Armed Forces. The weapon was introduced in 1984 to address a lack of sustained automatic fire capability at the squad level. The M249 SAW combines the rate of fire of a machine gun with the accuracy and portability of an assault rifle.

The M249 SAW is gas operated and air-cooled. It features a quick-change barrel (enabling the operator to rapidly replace an overheated or obstructed barrel) and a folding bipod attached to the front of the weapon (an M192 LGM tripod is also available.) The M249 SAW is normally belt-fed, although it is technically compatible with STANAG magazines (such as those used in the M16 and M4).

The M249 SAW has seen action in major conflicts involving the United States since the U.S. invasion of Panama in 1989. In 2009, the United States Marine Corps selected the M27 Infantry Automatic Rifle to partially replace the M249 in USMC service.

In 2022, the U.S. Army selected the SIG Sauer XM250 to replace the M249 SAW.

In 1965, the U.S. Army and U.S. 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 general-purpose machine gun, intended to be carried by troops to provide heavy automatic fire.

Both firearms were very heavy and usually required a crew of at least two in order to operate efficiently. The Browning automatic rifle (BAR), the army's main individual machine gun since its introduction in World War I, 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 fully automatic 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 were not designed with sustained automatic fire in mind, they often overheated or jammed. The 20-round and 30-round magazines of these weapons 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. Through the 1960s, the introduction of a machine gun into the infantry squad was examined in various studies. Most light machine gun experiments concentrated on the Stoner 63 light machine gun, a modular weapon that could be easily modified for different purposes. The Stoner 63 LMG saw combat for a brief period in Vietnam with the Marine Corps, and later on a wider scale with the U.S. Navy SEALs.

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

Actual design for alternative LMG cartridges did not begin until July 1971. A month later, Frankford Arsenal decided on two cartridge designs for the new LMG: a 6 mm cartridge and a new 5.56 mm cartridge with a much larger case. Neither design was finalized by March 1972, when the Army published the specifications document for the planned SAW. The 6 mm cartridge design was eventually approved in May of that year.

Prior to July 1972, SAW development contracts were awarded to Maremont, Philco Ford, and the Rodman Laboratory at Rock Island Arsenal, which produced the XM233, XM234, and XM235, respectively. Designs were required to weigh less than 20 lb (9.1 kg) including 200 rounds of ammunition, and have a range of at least 800 m (870 yd).

Three 5.56 mm candidate weapons were included with the 6 mm candidates in initial trials: the M16 HBAR; the Fabrique Nationale de Herstal (FN) Minimi; and the HK 23A1. Initial trials ended in December 1974. In February 1976, the Minimi and XM235 were selected for further development, and other designs were eliminated. Opinions on the 6 mm cartridge were mixed due to the logistical implications of having multiple calibers in infantry service.

In June, it was requested that the SAW specifications document be revised to emphasize standard 5.56 mm ammunition. In October, the requested revisions were approved, and bids were solicited for the conversion of the Rodman XM235 to 5.56 mm. Production of the converted XM235 was awarded to Ford Aerospace, and its designation was changed to XM248. A new M16 HBAR variant, the XM106, was developed in 1978, and soon after, Heckler & Koch lobbied to include a 5.56 mm conversion of its HK 21A1, instead of the standard 7.62 mm NATO ammunition it was built for, in future SAW testing. The latter model was designated the XM262. At this time, the Minimi received the designation XM249. Testing of the four candidates resumed in April 1979.

In May 1980, the FN XM249 was selected as the best choice for future development on the grounds of performance and cost, while the HK XM262 reportedly came a close second. In September, FN was awarded a "maturity phase" contract for further development of the XM249, and testing of the new weapon began in June 1981. The official adoption took place in February 1982.

The FN Minimi entered U.S. Army service as the M249 SAW in 1984, and was adopted by the U.S. Marine Corps in 1985. The U.S. production model has a different butt from that of the regular Minimi. It is manufactured in the FN factory in Columbia, South Carolina.

Although found to be reliable and accurate, multiple safety hazards were identified in the design, including sharp edges and an exposed hot barrel. Soldiers complained that the front sight required special tools to be adjusted. On August 23, 1985, then-U.S. Under Secretary of the Army James R. Ambrose suspended M249 production pending the development of a product improvement program (PIP.) Congress removed funds for the M249 from the Fiscal Year 1986 defense budget, then retroactively set aside the program's funding for other purposes. Over 1,100 M249s already issued were to remain in use, but be retrofitted with the PIP kit when it became available. Over 7,000 M249s were to stay in storage at depots until corrective changes could be made. The PIP kit was eventually developed and implemented, and production of the M249 resumed. In 1994 the M249 squad automatic weapon was re-designated the M249 light machine gun.

Initial reactions to the gun were mixed: it fulfilled the light machine gun role well when fired from a prone position, but was not as effective when fired from the shoulder or hip. It was praised for its extreme durability and massive firepower, but was criticized for a number of issues: the blank firing adapter fitted poorly, the bipod was fragile, the sling attachment was awkward, and there were many slots and gaps that accumulated dirt. Some claimed that the heavy-barrelled version of the M16 rifle was a more effective light machine gun.

The M249 SAW was not used consistently before the 1991 Gulf War, though it has been used in every major U.S. conflict since. American personnel in Somalia in 1993, Bosnia in 1994, Kosovo in 1999, Afghanistan in 2001 and Iraq since 2003 have been issued M249s. Surplus weapons were donated to Bolivia, Colombia and Tunisia.

Tactically, SAWs are either carried with a maneuvering unit and fired while handheld, or positioned to remain stationary and provide covering fire for other units. The base load of ammunition was originally 600 rounds, carried in three 200-round boxes. These boxes were carried in soft pouches labeled Case, Small Arms, Ammunition, 200-Round Magazine. The modern load of ammunition carried for the weapon is 1,000 rounds in five 200-round belts, although up to 500 extra rounds may be loaded into 100-round soft pouches.

A supply of 929 M249 SAWs was issued to personnel from the U.S. Army and Marine Corps during the Persian Gulf War. Although 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 weapons clogging up with sand after prolonged use in the desert environment.

The standard squad automatic weapon in Afghanistan was the M249 with PIP kit, which served alongside its heavier counterpart, the M240 machine gun. Most M249s were given a collapsible buttstock immediately prior to the invasion to reduce its length and make the weapons more practical for parachuting and close-quarters combat. Special Operations troops typically favored the shorter Para version of the weapon, which weighs much less.

A report entitled Lessons Learned in Afghanistan was released by Lieutenant Colonel Charlie Dean and SFC Sam Newland of the U.S. Army Natick Soldier Center in 2002. They found that 54% of SAW gunners had problems maintaining their weapons, and 30% reported that the gun rusted easily. Soldiers reported ammunition boxes rattling and falling off. 80% percent 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.

The PIP and Para versions of the M249 were used in the Iraq war since the invasion. By 2004, many M249s had been in service for almost 20 years and were becoming increasingly unreliable. Soldiers were requesting replacements and new features, and there are reports of soldiers holding their weapons together with duct tape. The lethality of the 5.56 mm ammunition has been called into question by reports of enemy soldiers still firing after being hit multiple times. As in previous conflicts, the sandy environment causes the M249s and other weapons to clog up and jam if they are not cleaned frequently.

Operation Iraqi Freedom PEO Soldier Lessons Learned, a report on the performance of weapons in the Iraq War, was published by Lieutenant Colonel Jim Smith of the U.S. Army in May 2003. Smith spoke positively of the M249, claiming that it "provided the requisite firepower at the squad level as intended". He praised the SPW variant, noting that its "short barrel and forward pistol grip allowed for very effective use of the SAW in urban terrain". At the National Defense Industrial Association in 2007, Lieutenant Colonel Al Kelly of the 1st Battalion, 17th Infantry gave a presentation describing the M249 as having "good range, excellent reliability" and an "excellent tracer". He said that a cloth pouch was preferred over the plastic box for holding linked ammunition, and that "knock-down power is poor, but is compensated by rate of fire".

In December 2006, the Center for Naval Analyses (CNA) released a report on U.S. small arms in combat. The CNA conducted surveys on 2,608 troops returning from combat in Iraq and Afghanistan over the past 12 months. Only troops who fired their weapons at enemy targets were allowed to participate. Three hundred forty-one troops were armed with M249 SAWs, making up 13 percent of the survey. 71 percent of M249 users (242 troops) reported that they were satisfied with the weapon. 40 percent of users preferred feeding the SAW with the soft 100-round pouch, while 21 percent chose the soft and hard 200-round pouches each. 60 percent (205 troops) were satisfied with handling qualities, such as handguards, size, and weight. Of those dissatisfied, just under half thought that it was too heavy. M249 users had the lowest levels of satisfaction with weapon maintainability at 70 percent (239 troops), most due to the difficulty in removing and receiving small components and poor corrosion resistance. The SAW had the highest levels of stoppages at 30 percent (102 troops), and 41 percent of those that experienced a stoppage said it had a large impact on their ability to clear the stoppage and re-engage their target. Sixty-five percent (222 troops) did not need their machine guns repaired while in theater. Sixty-five percent (222 troops) were confident in the M249's reliability, defined as level of soldier confidence their weapon will fire without malfunction, and 64 percent (218 troops) were confident in its durability, defined as level of soldier confidence their weapon will not break or need repair. Both factors were attributed to high levels of soldiers performing their own maintenance. 60 percent of M249 users offered recommendations for improvements. Seventeen percent of requests were for making the weapon lighter, and another 17 percent were for more durable belt links and drums, as well as other modifications, such as a collapsible stock.

In 2009, the U.S. Marine Corps selected the M27 Infantry Automatic Rifle, a lighter, magazine-fed rifle to supplement and partially replace the M249. With plans to buy up to 4,100 IARs to complement and partially replace its 10,000 M249s, of which 8,000 will remain in service, held at platoon level, it acquired 450 of the Heckler & Koch HK416–based weapons for testing. The Marines started fielding the M27 in 2010, but kept both weapons in the inventory due to the M249's greater ammunition capacity and higher sustained fire rate. Rifle companies are typically issued 27 IARs and six SAWs. The Army passed on the concept of the IAR, believing automatic rifle with a magazine would lower the effectiveness and firepower of a squad. While the Marine Corps has 13-man squads, the Army organizes its soldiers into squads of nine and needs considerably more firepower from the squad machine gunners to make up the difference.

The Army recognized the limitations of the M249, and in early 2017, the U.S. Army posted a notice soliciting bids for the Next Generation Squad Weapon-Automatic Rifle (NGSW-AR or NGSAR) to replace the M249. In July 2018, the Army awarded contracts to six companies including Textron, head of the preceding LSAT program where they made development leaps with cased telescoped (CT) ammunition, for NGSW-AR and ammunition prototypes. The stated requirements included:

• Maximum weight of 5.4 kilograms (12 lb), including sling, bipod, and sound suppressor
• Maximum total length of 89 centimeters (35 in)
• Engage pinpoint targets up to 600 meters (2,000 ft), and suppress (area fire targets) to a range of 1,200 meters (3,900 ft)
• Compatible with next-generation Small Arms Fire Control systems

In April 2022, the U.S. Army selected SIG Sauer as the winner of the competition. Their automatic rifle is designated the XM250.

The M249 SAW is a belt-fed light machine gun. It fires the 5.56×45mm 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. The M249 can also fire rifle grenades.

It fires from an open bolt and is gas operated. When the trigger is pulled, the bolt and bolt 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 spent casing as well as advance the belt and compress the recoil spring, thus preparing for subsequent shots. At 41 in (1,041 mm) long and 17 lb (8 kg) in weight (22 lb (10 kg) including a 200-round belt and plastic ammo box), the M249 is a cumbersome weapon.

The M249's air-cooled barrel is equipped with a mechanism to remove and replace the barrel assembly with a spare, this makes it easy for the operator to easily change the barrel on the field when it gets too hot during extensive amounts of fire. The barrel has a rifling twist rate of one turn in 180 mm (7 in). A folding bipod with adjustable legs is attached near the front of the weapon, though there are provisions for hard-mounting to a M192 Lightweight Ground Mount tripod or vehicle mount.

The M249's original gas regulator featured two different gas port sizes; normal and adverse. The normal gas setting has a cyclic rate of fire of around 850 rounds per minute, while the adverse gas setting increases the cyclic rate of fire to around 950–1,150 rounds per minute and is only used in extreme environmental conditions or when heavy fouling is present in the gas tube. The two-position gas regulator was discarded as part of a product improvement program, which made the M249s that received the product improvement kit no longer able to fire at the higher cyclic rate. The rapid rate of fire is around 100 rounds per minute. The sustained rate of fire, the rate at which the gunner can fire continuously without overheating, is around 50 rounds per minute.

The product improvement program (PIP) kit replaced the original steel tubular stock with a plastic stock based upon the shape of the heavier M240 machine gun. The change in stocks allowed for the addition of a hydraulic buffer system to reduce recoil. In addition, the dual gas port settings were reduced to only one; M249s with the product improvement kit can no longer fire at a higher cyclic speed. A handguard was added above the barrel to prevent burns, and the formerly fixed barrel changing handle was swapped for a folding unit. Certain parts were bevelled or chamfered to prevent cutting soldiers' hands and arms. Other changes involved the bipod, pistol grip, flash suppressor, and sights. 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 pouches" (to replace the original plastic ammunition boxes), and Picatinny rails for the feed tray cover and forearm so that optics and other accessories may be added.

An extensive maintenance program intended to extend the service life of M249 SAWs has been carried out, especially units that suffered from wear due to heavy use. In particular the warping of the receiver rails on the early models was a defect that occurred in heavily used first-generation M249s. This defect however has been eliminated on later models and is no longer present on the current-issue M249, which has reinforced rails and full-length welding rather than spot welding. A replacement of the M249's buttstock that is redesigned to be adjustable in length is also available.

The M249 Para (Paratrooper) is a compact version of the M249 SAW intended for use in airborne infantry units. It features a sliding aluminum buttstock, a shorter 13.7 in (348 mm) barrel, a length of 893 mm (35 in) and a weight of 7.1 kg (16 lb).

The M249 SPW (Special Purpose Weapon) is a modified version of the M249 SAW designed to meet United States Special Operations Command requirements. The barrel handle, magazine well, and mounting lug were removed to reduce weight. As a result, the SPW cannot be mounted in vehicles or use STANAG magazines. Picatinny rails were added to the feed cover and forearm to accommodate SOPMOD accessories. The weapon also features a detachable bipod. The SPW's lightweight barrel is longer than that of the Para model, giving it a total length of 908 mm (36 in) and a weight of 5.7 kg (13 lb).

The Mk 46 is a further development of the M249 SPW that features minor changes. The program that led to both the Mk 46 and Mk 48 was headed by the US Naval Special Warfare Command (NAVSPECWAR.) The Mk 46 retains the standard M249 SAW plastic buttstock instead of the collapsible buttstock used on the SPW. The Picatinny rail forearm differs slightly from the SPW. The Mk 46 has the option of using the lighter SPW barrel or a thicker, fluted barrel of the same length.

The Mk 48 is a variant of the Mk46 rechambered in 7.62×51mm NATO. It is officially classified as an LWMG (Light Weight Machine Gun) and was developed as a replacement for the Mk 43 Mod 0/1, itself a variant of the M60 machine gun. Reliability issues with the M60 and its design variants led the US Army to replace it with the M240B in the mid-1990s. The M240B, however, weighs in at a considerable 27.5 lb (12.5 kg) and is about 49 in (120 cm) long with the standard barrel. NAVSPECWAR was reluctant to give up the increased portability of the M60 (which weighed 22.5 lb (10.2 kg) with an overall length of 37.7 in (96 cm) in its shortest configuration) in spite of the M240B'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 SAW weighing in at 18.5 lb (8.4 kg) with an overall length of 39.5 in (100 cm). The new design achieved improved reliability compared to M60 variants with a decrease in weight. USSOCOM was expected to receive deliveries of the new variant in August 2003.

The M249S is a semi-automatic only variant manufactured for the civilian sport and collector's market. It shares most major components of the M249 SAW with the exception of the firing mechanism and the addition of welded internal components to prevent automatic conversion. Notably, this variant retains the ability to be belt fed, an uncommon feature in civilian firearms.

•  Afghanistan
•  Argentina
•  Colombia
•  Czech Republic
•  Georgia
•  Hungary
•  Iraq
•  Lebanon
•  Kurdistan
•    Nepal
•  Philippines
•  Thailand
•  United States

•  Islamic Republic of Afghanistan: Standard issue light machine gun of the Afghan National Army

• List of dual-feed firearms
• List of machine guns

• Daewoo Precision Industries K3 – (South Korea)
• Heckler & Koch MG4 – (Germany)
• IWI Negev – (Israel)
• PK machine gun – (Soviet Union)
• RPL-20 – (Russia)
• Third Arm Weapon Interface System – (United States)
• Ultimax 100 – (Singapore)

Government publications

• FN M249 webpage by FN America
• FN M249 webpage by the U.S. Army
• FN M249 webpage by the FAS Military Analysis Network
• FN M249 webpage at Nazarian.no