The M27 Infantry Automatic Rifle is a Light Machine Gun produced by Heckler and Koch . It was designed as a support weapon variant of the HK 416 Assault Rifle, and is compatible with standard 5.56mm STANAG magazines. It is currently in USMC service alongside the M249 and M240.
"This beefed up M416 entered service alongside the M249 in the Marine Corps in 2011. The M27 Infantry Automatic Rifle (IAR) features a heavier, longer barrel and an extended magazine to enable greater amounts of suppressive fire while retaining some of the mobility of a standard M416. The M27 features a bipod by default for supported shooting."
The M27 is the default light machine gun for the United States Marine Corps' Support kit, and is unlocked later for both factions at 170,000 Support score. Like the other LMGs, it comes pre-equipped with a bipod. The M27 functions almost exactly the same to the M416 (its assault rifle variation) sharing iron sights, reload animations with the M27 having larger barrel and magazine size, and a comparable overall appearance; it also shares the same fire rate, damage, and a similar recoil profile.
Unlike other light machineguns, the M27 has a smaller magazine size, at 45+1 rounds, and a much faster reload, faster than any light machine guns, as it is fed by box magazines rather than belts. The June 4, 2012 patch allowed the M27 to utilize the extended magazine and heavy barrel after obtaining 300 and 350 kills respectively.
The 416 Carbine and M27 IAR are identical to each other, apart from the larger magazine and unusable Bipod attached to the latter.
The M27 IAR also has a different reloading animation from the 416 Carbine. While the latter has the player pull the charging handle at the end, the former has the player hitting the bolt release instead.