BAE Systems will overhaul two MK 45 Mod 4 naval guns at its facility in Louisville, Kentucky.

The US Navy will pay BAE Systems $38.2 million to overhaul two MK 45 Mod 4 naval guns.

The multi-mission MK 45 Mod 4 Naval Gun System is the lightest, most compact, widely deployed 27 mm gun in service today. More than 260 units have been delivered to the US Navy, which uses them as the main armament on its Arleigh Burke-class destroyers and Ticonderoga-class cruisers, and nearly a dozen allied navies, according to The Defence Blog. Other navies that use the gun system include Australia, Denmark, Japan, and South Korea.

The Development of Mark 45 Naval Gun

FMC Corporation, whose defense division later became United Defense, started developing the gun in the 1960s. It was designed for anti-surface, strike, and anti-air warfare. 

The US Navy first deployed the MK 45 Mod 0 aboard its Spruance-class destroyers in 1971. It has been steadily updated over more than five and a half decades of service. BAE Systems bought United Defense in June 2005, and took over manufacturing, overhauls, and upgrades to the MK 45.

Work on the guns will be completed at BAE Systems’ facility in Louisville, Kentucky, and completed by March 2030.

About the Mark 45 Naval Gun 

The MK 45 Mod 4 is noted for its 127 mm (5-inch) diameter barrel with an extended 62-caliber barrel length that provides for higher muzzle velocity and range. The gun has a firing rate of 16 to 20 rounds per minute and can strike targets at more than 20 nautical miles (23 mi, or 36 km) when using extended-range or “cargo” projectiles with enhanced propelling charges. The gun features a fully digital control architecture with a touch-screen user interface; that lowers crew interaction, with automated ammunition handling and remote firing systems increasing the rate of fire.

A structurally strengthened gun mount on the Mod 4 version has increased the firing energy by 50 percent over the older .54-caliber variant, which in turn has enabled munitions to travel faster and farther. The gun system was also designed with low-maintenance requirements and a reduced-radar-cross-section (RCS) flat-panel gun shield.

The Largest Gun in Use with the US Navy

The MK 45 Mod 4 is currently the largest surface gun employed by the US Navy on its warships. It is a sign of the times that bigger guns aren’t needed—as missiles can accomplish much of the heavy hitting with far greater accuracy and to far longer ranges.

As a “5-inch” gun, the MK 45 is almost tiny compared to the Mark 7 guns that were on the US Navy’s Iowa-class battleships. Each of those guns was 16 inches (40.6 cm), with a barrel length of 66 feet (50 calibers long), and was able to fire 2,700 pound (1,225 kg) “super-heavy” armor-piercing shells, employing 660 pounds of black powder to launch the projectile to ranges of up to 24 miles (38 km).

For a while, the MK 45 was eclipsed by the 155 mm (6.1-inch) Advanced Gun System (AGS) developed for the US Navy’s Zumwalt-class destroyers. However, as the specialized ammunition became too expensive, the guns were subsequently removed from the warships—leaving the MK 45 Mod 4 as the US Navy’s current biggest gun!

About the Author: Peter Suciu

Peter Suciu has contributed to dozens of newspapers, magazines and websites over a 30-year career in journalism. He regularly writes about military hardware, firearms history, cybersecurity, politics, and international affairs. Peter is also a contributing writer for Forbes and Clearance Jobs. He is based in Michigan. You can follow him on Twitter: @PeterSuciu. You can email the author: Editor@nationalinterest.org.

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