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 U.S. 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 gun 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 an 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 1989 invasion of Panama. Soldiers are generally satisfied with the weapon's performance, though there have been reports of clogging with dirt and sand. Due to the weight and age of the weapon, the United States Marine Corps is testing the M27 Infantry Automatic Rifle with plans to partially replace the M249 in Marine Corps service.
Development
In 1965, the U.S. Army and 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.Browning automatic rifle, 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.[7][8] 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 "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.
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.[10] While there was a brief flirtation with the concept of a flechette- or dart-firing Universal Machine Gun during one study, most light machine gun experiments concentrated on the Stoner 63 light machine gun, a modular weapon which could be easily modified for different purposes.[11][12] The Stoner 63 LMG saw combat for a brief period in Vietnam with the USMC, 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 caliber cartridges for the LMG did not appear until 1969.[14] In July 1970, the U.S. Army finally approved development of an LMG, with no specified calibre. At this time, the nomenclature "Squad Automatic Weapon" (SAW) was introduced. Actual design of alternative cartridges for the LMG did not begin until July 1971. A month later, Frankford Arsenal decided upon 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.[16][17] Prior to July 1972, SAW development contracts were awarded to Maremont, Philco Ford, and the Rodman Laboratory at Rock Island Arsenal. These companies produced designs with Army designations XM233, XM234 and XM235 respectively—X denoting "experimental". Designs were required to have a weight of less than 9.07 kg (20 lb) including 200 rounds of ammunition, and a range of at least 800 meters (2,600 ft). The 6 mm cartridge design was eventually approved in May that year.
When the time came for developmental and operational testing of the SAW candidates, three 5.56 mm candidate weapons were included with the 6 mm candidates: the M16 HBAR, a heavy-barrel variant of the M16 designed for prolonged firing; the Fabrique Nationale de Herstal (FN) Minimi; and the HK 23A1. The initial round of tests ended in December 1974.[18] In February 1976, the Minimi and Rodman XM235 SAW were selected for further development. At this time, opinions of the 6 mm cartridge were beginning to sour due to the logistical implications of providing yet another ammunition type to the infantry. 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 on February 1, 1982.
The new gun entered U.S. Army service as the M249 squad automatic weapon in 1984, and was adopted by the U.S. Marine Corps a year later. 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, the M249 was considered to present unacceptable hazards in the form of an exposed hot barrel and sharp edges. There were also complaints that the front sight required special adjustment tools. On August 23, 1985, Undersecretary of the U.S. Army James R. Ambrose Congress deleted funds for the M249 from the Fiscal Year 1986 defense budget, then retroactively set aside the program's prior year's funds from the M249 program for other purposes, including retirement and pay raises. 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 remaining 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.suspended M249 production pending the development of the product improvement program (PIP) intended to fix these problems.
Design details
A U.S. Marine firing an M249 from an M122A1 at a training range.
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 1,041 mm (41 in) long and 7.5 kg (17 lb) in weight (10 kg (22 lb) including a 200-round belt and plastic ammo box), the M249 is a cumbersome weapon.
The barrel has a rifling twist rate of one turn in 180 mm (7 in). Because firing heats up the bore, the air-cooled barrel is equipped with a mechanism to remove and replace the barrel assembly with a spare.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 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 750 rounds per minute (r/min) or 1,000 r/min. The latter setting was intended for adverse conditions such as an excessively dirty firearm or cold weather. The two-position gas regulator was discarded as part of a product improvement program. Sustained rate of fire, the rate of fire at which the gunner can fire continuously without overheating, is approximately 85 r/min.
| M1918 BAR Retired U.S. LMG | M249 U.S. LMG | M249 Para U.S. LMG | M16A2 U.S. Service Rifle | M240B U.S. MMG | RPK-74 Russian LMG | Negev[30] Israeli LMG | Ultimax 100 Singaporean LMG | |
|---|---|---|---|---|---|---|---|---|
| Weight loaded | 9.5 kg (21 lb) | 10 kg (22 lb) | 9.1 kg (20 lb) | 4 kg (9 lb) | 15.8 kg (35 lb) | 5.56 kg (12 lb) | 9.7 kg (21 lb) | 6.8 kg (15 lb) |
| Length | 1,194 mm (47 in) | 1,041 mm (41 in) | 893 mm (35 in) | 1,000 mm (39 in) | 1,245 mm (49 in) | 1,060 mm (42 in) | 1,020 mm (40 in) | 1,030 mm (41 in) |
| Cartridge | 30-06 Springfield | 5.56x45mm NATO | 5.56x45 mm NATO | 5.56x45 mm NATO | 7.62x51 mm NATO | 5.45x39 mm | 5.56x45 mm NATO | 5.56x45 mm NATO |
| Ammunition feed | 20-round box mag | 200-round belt | 200-round belt | 30-round box mag | 100-round belt | 45-round box mag | 150-round belt | 100-round drum |
| Muzzle velocity | 860 m/s (2,820 ft/s) | 915 m/s (3,000 ft/s) | 915 m/s (3,000 ft/s) | 930 m/s (3,050 ft/s) | 905 m/s (2,970 ft/s) | 960 m/s (3,150 ft/s) | 915 m/s (3,000 ft/s) | 970 m/s (3,180 ft/s) |
Variants
- M249 PIP
- The product improvement program 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; variants 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 carrying handle was swapped for a folding unit. Certain parts were beveled 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 pack" magazines (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.
- M249 Para
- 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 at 893 mm (35 in) long and 7.1 kg (16 lb) in weight. 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 mounting lug all have 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 the mounting of optics, lasers, vertical foregrips, and other M4 SOPMOD kit accessories. The SPW also has 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).
- Mk 46 Mod 0
- 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 (NAVSPECWAR). 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. The Picatinny rail forearm also 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.
- Mk 48
Main article: Mk 48 machine gun
- This is a 7.62x51 mm NATO version of the Mk 46, used by USSOCOM, when a heavier cartridge is required.[35] 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 lb and is about 49" long with the standard barrel. NAVSPECWAR was reluctant to give up the increased portability of the M60 (~22.5 lb, 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 ~18.5 lb 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.
Machine Gun, 5.56 mm, M249
M249 ParaType Squad automatic weapon/Light machine gun Place of origin Belgium (FN Minimi)
United States (M249 derivative)
Service history In service 1984–present Used by United States Armed Forces, U.S. Diplomatic Security Service (DSS), and Lebanon[1] Wars Invasion of Panama
Persian Gulf War
Unified Task Force
Bosnian War
Kosovo War
Afghan War
Iraq War
Production history Designed 1976 Manufacturer Fabrique Nationale de Herstal Unit cost US$4,087[2] Produced late 1970s–present Variants See Variants Specifications Weight 7.5 kg (17 lb) empty,
10 kg (22 lb) loadedLength 1,041 mm (41 in) Barrel length 521 mm (21 in) Cartridge 5.56x45 mm NATO Action Gas-operated, open bolt Rate of fire 750–1,000 rounds per minute Muzzle velocity 915 m/s (3,000 ft/s) Effective range 1,000 yd (910 m) Feed system M27 linked belt, STANAG magazine
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