The M2 was a large-caliber heavy machine gun, usually mounted on vehicles or in fixed emplacements. Marine Corps' primary machine guns were the M2 Browning and M60. Army selected the Sig Sauer XM250 to replace the M249. Marine Corps selected the M27 Infantry Automatic Rifle, to partially replace the M249 in USMC service. M249s have seen action in major conflicts involving the United States since the U.S. The STANAG magazines should only be used in emergencies, however, due to their high malfunction rate. 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 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 attached to the front of the gun (an M192 LGM tripod also being available). The M249 provides infantry squads with a high rate of machine gun fire, combined with the accuracy and portability of a rifle. 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 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. The M249 light machine gun ( LMG), also known as the M249 Squad Automatic Weapon ( SAW), which continues to be the manufacturer's designation, 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). Iron sights or Picatinny rail for various optics M27 linked disintegrating belt, STANAG magazine

M27 infantry automatic rifle