Infantry guns are artillery weapons for the use of infantry units. The designs usually have short barrels which fire a low speed shell. They are lightly built so they are easy to moved around on the battlefield. Very few infantry guns are still used by infantry units. They have been replaced by grenade launchers, light anti-tank weapons and heavier wire-guided missiles. Pack guns are similar to an infantry gun, but mean those guns that are meant to be taken apart for movement. Mountain guns are infantry guns designed for use during mountain combat. Airborne guns are those designed for use by paratroopers. They are easy to move and lighter weight when compared to field guns.