3rd Assault Amphibian Battalion (3rd AABn) is one of two active duty assault amphibian battalions in the United States Marine Corps. The battalion's primary weapon system is the Amphibious Assault Vehicle or AAV. The AAV is a 27.5-ton armored vehicle that carries up to 21 combat-loaded Marines and is armed with the UGWS (UpGunned Weapons Station), which mounts a .50 cal (12.7 mm) M2HB machine gun and a Mk-19 40 mm grenade launcher. The battalion is also equipped with the Amphibious Combat Vehicle or ACV, a rather new variant to the USMC’s amphibious armament which will replace the AAV in years to come. The AAV ACV are the only armored vehicles in the U.S. inventory that are fully capable of operations both on land and in the ocean. The battalion is part of the 1st Marine Division and the I