M249 SAW 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 . Development . 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 . 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 . Variants . 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 . 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 . 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 . Afghanistan . 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 .