A student with Company D, Infantry Training Battalion – East looks down range after firing the M27 Infantry Automatic Weapon aboard Marine Corps Base Camp Lejeune Jan. 9. The IAR is meant to replace the M249 Squad Automatic Weapon, giving Marines a lighter, more precise weapon to use while deployed. - A student with Company D, Infantry Training Battalion – East looks down range after firing the M27 Infantry Automatic Weapon aboard Marine Corps Base Camp Lejeune Jan. 9. The IAR is meant to replace the M249 Squad Automatic Weapon, giving Marines a lighter, more precise weapon to use while deployed.