The MK38 is the naval version of the M242, it equip the US Navy, with nearly 4,000 copies in 2012. The Mk 38 consists of the M242 chain gun and the Mk 88 Mod 0 machine gun mount. It provides ships with defensive and offensive gunfire capability for the engagement of a variety of surface targets. Designed primarily as a close-range defensive measure, it provides protection against patrol boats, floating mines, and various shore-based targets.
The M242 is currently in use by the United States Army, Navy, Marine Corps, and Coast Guard.
The M242 Bushmaster is a 25 mm (25×137mm) chain-driven autocannon. It is used extensively by the U.S. military, as well as by NATO’s and some other nations’ forces in ground combat vehicles, such as the Bradley fighting vehicle and various watercraft. Originally the weapon was designed and manufactured by Hughes Ordnance in Culver City, CA, which was acquired by McDonnell Douglas (later acquired by the Boeing Corporation); however it is now produced by Alliant Techsystems (ATK) of Mesa, Arizona.
It is an externally powered, chain-driven, single-barrel weapon which may be fired in semi-automatic, burst, or automatic modes. It is fed by a metallic link belt and has dual-feed capability. The term “chain gun” derives from the use of a roller chain that drives the bolt back and forth. The standard rate of fire is 200 rounds per minute. The weapon has an effective range of 3,000 metres (9,800 ft), depending on the type of ammunition used. With over 10,000 units sold worldwide, it is one of the most successful modern autocannons.