The M249, aka, SAW (Squad Automatic Weapon) has been a staple weapon of the US military since the end of Vietnam, when it replaced the M60 (or as it was better known, the Pig). Advantages over the M60 include a shorter barrel, a lighter overall weight, and reduced susceptibility to barrel heating after prolonged firing.
The M249 can be belt or magazine fed. Standard box magazines for the weapon contain 200 rounds of ammunition. Effective range for engaging an area target is about 1 kilometer. The weapon is designed for suppressive fire, and supports a bi-pod for that function.
The original version of the weapon was called the Minimi, produced by the Belgium weapons manufacturer FN. The United States military officially adopted the Minimi and designated it the M249 in the early 1980's.
The M249 rarely reflects its real life counterpart in video games. Because of the difficulty in depicting the heft and consequential fatigue of carrying the weapon, it often just acts as a close quarters weapon with a large magazine. Expanding target reticules have recently encouraged players to drop into a prone position to maintain accuracy, but this effect does not prevent players from walking down hallways spraying the weapon's bullets at random. This effect also lacks the dynamic function of the real weapon, as the bi-pod cannot be used on raised positions.
The Para version of the M249 is a compact version of the gun with a shorter barrel, making it ideal for airborne troops.