The M249 Squad Automatic Weapon (M249 SAW) is the United States military designation for a sub-family of the FN Minimi. The M249 is an air-cooled, gas-operated, fully-automatic-only firearm that fires from an open bolt position.

It can accept belts of linked 5.56x45mm NATO (.223) ammunition through the top-mounted feed tray or M16-type magazines through the side-mounted port. The latter allows a SAW gunner to use riflemens' magazines in an emergency if he runs out of belted ammunition, though this often causes jams as the magazine spring cannot adequately keep up with the weapon's high rate of fire.  The M249 SAW features a built-in bipod and a tripod-mounting lug for supported fire, as well as a quick change barrel that helps prevent overheating during sustained fire, capable of delivering a large volume of effective fire to support infantry squad operations.

Effective ranges include 600 m for a point target, 800 m for an area target, and 1,000 m for suppression. Tracer ammunition burnout is at 900 m, however. The advised rates of fire are 85 rounds per minute with no barrel changes. With a barrel change every two minutes, this increases to 200 rounds per minute. For a barrel change every minute, the rate of fire can go up to 850 rounds per minute, which is approximately equal to the cyclic rate of fire, at about 850 to 900 round/min.