How a FN M249 SAW Works

Wikipedia: The M249 light machine gun (LMG), also known as the M249 Squad Automatic Weapon (SAW),[3][4] which continues to be the manufacturer's designation,[5] and formally written as Light Machine Gun, 5.56 mm, M249, is the American adaptation 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 by the subsidiary FN Manufacturing LLC, a company in Columbia, South Carolina, and is widely used in the U.S. Armed Forces. The weapon was introduced in 1984 after being judged most effective (compared to a number of candidate weapons) to address the lack of automatic firepower in small units. The M249 provides infantry squads with a high rate of machine gun fire, combined with the accuracy and portability 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), and a folding bipod attached to the front of the weapon (an M192 LGM tripod also being available). The SAW can be fed from both linked ammunition and STANAG magazines (such as those used in the M16 and M4), allowing the SAW operator to use them as a source of ammunition in case they run out of belts. The STANAG magazines should only be used in emergencies, however, due to their high malfunction rate.

M249s have seen action in major conflicts involving the United States since the U.S. invasion of Panama in 1989. In 2009, the U. S. Marine Corps selected the M27 Infantry Automatic Rifle, to partially replace the M249 in USMC service.[6] In 2022, the U.S. Army selected the Sig Sauer XM250 to replace the M249.

Type Light machine gun
Squad automatic weapon
Place of origin

Belgium (Minimi)
United States (M249)

Service history
In service 1984–present
Used by See Users
Wars

Invasion of Panama
Gulf War
Unified Task Force (Somalia)
Bosnian War
Kosovo War
War in Afghanistan
Iraq War
Syrian Civil War
Russo-Ukrainian War (2014–present)[citation needed]
Yemeni Civil War (2015–present)
Saudi-led intervention in Yemen

Production history
Designed 1976
Manufacturer FN Herstal
Unit cost US $4,087[1]
Produced Late 1970s–present
Variants See Variants
Specifications
Mass

7.5 kg (17 lb) empty
10 kg (22 lb) loaded with 200 rounds

Length 40.75 in (1,035 mm)
Barrel length

465 mm (18 in)
521 mm (21 in)

Cartridge 5.56×45mm NATO
Action Gas-operated long-stroke piston, opened rotating bolt
Rate of fire

Sustained:
100 rounds/min
Rapid:
200 rounds/min
Cyclic:
700–850 rounds/min
(gas setting 1: normal)
950–1,150 rounds/min[2]
(gas setting 2: adverse)

Muzzle velocity 915 m/s (3,000 ft/s)
Effective firing range

700 m (2,300 ft) (point target, 465 mm barrel)
800 m (2,600 ft) (point target, 521 mm barrel
3,600 m (11,800 ft) (maximum range)

Feed system M27 linked disintegrating belt, STANAG magazine
Sights Iron sights or Picatinny rail for various optics.