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MK 45 5-inch / 54-caliber (lightweight) gun
MK 45 5-inch / 62-caliber (MOD 4 ERGM) gun

The 5"/54 MK 45 Light Weight Gun Mount (LWGM) is the Navy's primary anti-surface gun battery, and Naval Gun Fire Support (NGFS) weapon. When a target is within the engagement envelope, the 5" gun is significantly more economical than a guided weapon. Versatile and extremely accurate, the gun is also used in an anti-air defense in depth capacity.

The 54-caliber (Mk 45) lightweight gun provides surface combatants accurate naval gunfire against fast, highly maneuverable surface targets, air threats and shore targets during amphibious operations. This lightweight gun system offers significant improvements in reliability and maintainability over the 54-caliber Mk 42 gun systems. The Mk 45 is controlled by either the Mk 86 Gun Fire Control System or the Mk 160 Gun Computing System. Range is more than 13 nautical miles and can fire 16-20 rounds per minute. Each magazine has a capacity of 475-500 rounds. The Mark 45 has been in service since 1971 witht the US Navy and Coast Guard.

The Naval Surface Fire Support (NSFS) program was developed in response to the Navy’s Forward From the Sea strategy and the Marine Corps’ Operational Maneuver From the Sea doctrine. Both of these documents described the need for a combination of various NSFS systems for close-in and over the horizon (OTH) amphibious operations with sufficient range, accuracy, and lethality to meet the wide range of requirements for the support of assaulting forces during all phases of the operation. The NSFS mission is not only for Naval Gunfire Support but also for suppression and destruction of hostile antiship weapons and air defense systems.

The two key elements of the NSFS program are the Extended Range Guided Munition EX 171 and the modified MK 45 MOD 4 gun mount. In conjunction with an increase in barrel length from 54 to 62 calibers and other gun modifications by United Defense, ERGM is expected to boost the 5-inch gun's range from 13 to 63 nautical miles. Due to the development of the EX 171, the existing 5" MK 45 mounts must be modified to support the new round. The EX 171 will be able to operate at greater ranges than existing 5" ammunition. Both elements are in their early phases of development. The NSFS system will be installed on DDG 52 class ships by the year 2001.

The Naval Surface Fire Support (NSFS) program at Indian Head Division of the Naval Surface Warfare Center has designed/developed a Proof of Concept (POC) propelling charge capable of launching a Extended Range Guided Munition (ERGM) from a 5-inch 62-caliber gun. The NSFS program was born from the Navy’s "From the Sea" maritime strategy and the Marine Corps’ "Operational Maneuver From the Sea" doctrine. As directed by the CNO Executive Board (CEB), a modification to the existing 5"/54 Mk 45 gun system was determined to be the best alternative to meet the near term needs. The modification included upgrading of the 5"/54 gun system to a 5"/62, design/development of an ERGM and the design/development of a high energy propelling charge.

Based on the current propelling charge performance, it was apparent that the Navy did not have a propelling charge that could be transitioned into a high performance charge. Navy senior propellant technologists, utilizing their extensive knowledge gained through the development of M43 propellant for the Army, suggested that a nitramine propellant would be the key to the goal. Pilot plant and production engineers were soon manufacturing what has evolved into a nitramine propellant. Introduction of a nitramine propellant required engineers to design a new bayonet-type primer specifically optimized for use with the propellant. This task was soon accomplished, and the new propellant and primer were married into the EX 167 propelling charge. The EX 167 has been gun tested and has shown that it is capable of launching ERGM-type projectiles from a 5-inch 62-caliber gun while staying below the gun operating pressure.

Raytheon TI Systems' ERGM is a rocket-assisted 5" projectile that will be fired from the 5"/62 MK 45 Mod 4 Gun Mount. It incorporates a rocket motor and internal Global Positioning System (GPS) coupled with an Inertial Navigation System (INS). The coupled GPS/INS will provide autonomous guidance and control to a fixed target location determined prior to firing. The rocket motor will provide range capability far in excess of current ballistic projectiles (Threshold range - 41 NM; Objective range - 63 NM). The warhead will consist of a highly effective submunition payload of 72 XM80 Dual Purpose Improved Conventional Munition (DPICM) over a selectable 20-100 meter area with 10-20 meter accuracy, thanks to GPS-aided guidance.. The combination of the extended range and GPS/INS position accuracy will provide significantly improved performance to meet NSFS mission requirements. A planned Improvement Program (P3I) is underway that will explore ways to expand ERGM's capabilities and reduce its cost. Beginning in 2002, about 50 Aegis cruisers and destroyers will be outfitted with the 5-inch/62-caliber ERGM capability.

Specifications

Primary Function Fully-automatic, lightweight gun mount.
Range 13 nautical miles (14.9 statue miles)
63 nautical miles - ERGM
Type of Fire 16-20 rounds per minute automatic
Magazine Capacity475-500 rounds per magazine.
Caliber 5 inch (12.7 cm)
Date Deployed 1971 (Mark 45)

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