The Mk 44 Bushmaster II is a derivative of the M242 Bushmaster cannon. The main difference is their caliber – 30 mm vs. 25 mm respectively, the barrel is chrome-plated for extended life. It uses some 70% of the same parts as the M242 while increasing the firepower by as much as 50% with the 20% increase in caliber size. It is the standard primary armament of Bionix-II AFV currently in service with the Singaporean Army, as well as that of the CV90 AFVs in Finnish, Norwegian, Polish, and Swiss service.
Since 2007, the United States Air Force has selected this cannon to replace the 25 mm and 40 mm guns on its fleet of AC-130U gunships. The United States Marine Corps’ Expeditionary Fighting Vehicle, which is presently undergoing tests and evaluations, is expected to be armed with this cannon as well.
Some United States Navy vessels, such as the San Antonio-class amphibious transport dock USS New York (LPD-21), are armed with the Bushmaster II for surface threat defense.