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MK-38 25-mm Machine Gun


The 25mm Machine Gun System (MGS) Mk-38 is a 25mm automatic gun system that provides ships with a defensive and offensive gunfire capability for the engagement of a variety of surface targets. It is designed to provide close range defense against patrol boats, swimmers, floating mines, and various targets ashore including; enemy personnel, lightly armored vehicles and terrorist threats. One crewman is required for operation and two for maintenance.


Also known as "Bushmaster," this weapon is a navalized version of the "Chain Gun," an externally-powered weapon developed by Hughes for the US Army as the Mk-242. The Mk-38 replaced the obsolete 20mm Mk-67 guns, which had high maintenance requirements. The Army's Mk-242 gun entered service in the 1970th. The Navy's Mk-38 followed in 1988.

Since then, the Mk-38 was employed aboard various combatant and auxiliary ships in the Middle East Force escort operations and during Operations Desert Shield and Desert Storm.

The Machine Gun System:

The Mk-38 guns are maintained in a rotatable pool, available for temporary installation on various deploying ships and permanent installation on certain amphibious and auxiliary ships, patrol craft and Coast Guard cutters.

This system consists of the M242 auto-cannon and the Mk-88 machine gun mount. The M242 auto-cannon is an externally powered, dual-feed, single-barrel weapon which may be fired in semi-automatic or automatic modes. In the automatic mode, the rate of fire is approximately 175 rounds per minute. The M242 does not depend on gases for operation but instead utilizes an electric motor, located in the receiver, to drive all the moving parts inside the cannon. Ammunition feeding, loading and firing, extraction, and ejection are all done by the motor. The Mk-88 machine gun mount train and elevation is controlled manually by the gun operator. In the event of a major malfunction, the M242 auto-cannon can be removed from the mount and another auto-cannon installed in five minutes by two people.

Due to the maximum elevation rate of 55 degrees the Mk-38 has only limited anti-air-warfare importance. Therefore, th Mk-38 is mainly used against surface targets like mines and boats.

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General Characteristics - Mk-38 25mm Machine Gun
Primary FunctionSingle barrel, air cooled, semi- and full-automatic, manually trained and elevated machine gun system
ContractorDesigned and assembled by Crane Division, Naval Surface Warfare Center;
components produced from various contractors
RangeMaximum: 7,450 yards (6,800 meters)
Effective: 2,700 yards (2,460 meters)
Guidance SystemUnstabilized, manually trained and elevated
WeightGun: 240 lbs. (109 kg)
Gun mount: 1,250 lbs. (567 kg)
Length of Barrel85.6 inch (2.175 meters)
Muzzle Velocity1,100 meters/second
Approx. Barrel Life25,000 rounds
Type of FireSingle shot;
175 rounds per minute automatic
Caliber1 inch (25mm)
Date Deployed1986

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