From Military Times:

Commandant Gen. Jim Amos has approved the full fielding of the M27 Infantry Automatic Rifle, a sleek, 5.56mm weapon that will become the new standard for automatic riflemen. There will be one IAR in virtually every four-man fire team, with three per squad, 28 per company and almost 4,476 across the Corps.

The IAR is a variant of Heckler and Koch’s HK416 assault rifle, which is popular with special operators and frequently used with suppressors. It weighs 9.2 pounds loaded, less than half the weight of SAW, made by FN Herstal. It has an adjustable butt stock and runs on standard 30-round magazines, although the Corps also is exploring the possibility of a high-capacity magazine that would carry between 50 and 100 rounds.