M27 Infantry Automatic Rifle

The IAR (Infantry Automatic Rifle) program was originally initiated by US Marine Corps in an apparent intent to replace aging M249 SAW light machine guns in their "automatic rifle" (squad automatic) role. USMC sought lighter and more maneuverable weapon, still capable of at least some sustained firepower. The Marine Corps is planning to purchase 4,476 IARs to replace 2,000 M249 light machine guns currently employed by automatic riflemen within Infantry and Light Armored Reconnaissance Battalions.

The M27 is based on the Heckler & Koch HK416, which in turn derives from the M4 carbine and Heckler & Koch G36. It features a gas-operated short-stroke piston action (instead of the traditional direct impingement) with a rotating bolt. The weapon also fires from a closed bolt position, unlike many traditional machine guns. It is modified with a heavier barrel and includes a bayonet lug. The free-floating barrel is surrounded by MIL-STD-1913 Picatinny rails for use with accessories and optics. It draws ammunition from any standard STANAG magazine.

Specifications
Weight : 7.9 lb (3.6 kg) empty
Length : 36.9 to 33 in (94 to 84 cm) w/ adjustable stock
Barrel length : 16.5 in (42 cm)
Width : 3.1 in (7.9 cm)
Height : 9.4 in (24 cm)
Cartridge : 5.56×45mm NATO
Action : Gas-operated short-stroke piston, rotating bolt
Rate of fire : 560 to 640 rpm
Feed system : 20-round or 30-round STANAG magazine
Sights : flip-up rear rotary diopter sight and front post, Picatinny rail