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4.5 inch (114 mm) Mark 8 naval gun

The 4.5 inch (114 mm) Mark 8 is a British naval gun system. The 4.5 inch gun has been the standard medium-gun calibre of the Royal Navy for use against surface, aircraft and shore targets since 1938. The current weapon replaced the earlier lineage of 4.5 inch guns. Like all British 4.5 inch guns, it actually has a calibre of 4.45 inches (113 mm). A 155mm variant is under development.

Design

A completely new type of 4.5 inch gun, it was designed in the 1960s for the Royal Navy's new classes of frigates and destroyers. The new weapon, built by Vickers, was developed by the Royal Armament Research and Development Establishment using the 105 mm gun-howitzer of the Abbot self-propelled gun as a starting point. The outer shell of the gunhouse is built from glass reinforced plastic (GRP).

The new weapon emphasised reliability over a high rate of fire, allowing a switch to a lighter, single barrel mounting and ammunition of a one-piece design.

The gun system has a combination of electrical and hydraulic components and the full system penetrates up to three deck levels below the weather deck; deep magazine, gun control room and power room, gunbay and the gunhouse.

The weapon is semi-automatic, therefore needing fewer people than its predecessors to operate. With no personnel in the gunhouse loading is supported by personnel in the gunbay to load the feed ring, the deep-magazine to pass ammunition to the gunbay. The Captain of the Gun in the control room ensures continued operability and the gun controller in the Operations Room operates the aiming and firing process. The weapon has a rate of fire of about 25 rounds per minute and a range of 12 nm (22 km).

The first recipient of the new gun and mount, the Mark 8, was the Iranian frigate Zaal in 1971. The gun entered Royal Navy service in 1973 on the new destroyer Bristol.

The first major modification to the mounting, the MOD 1, was developed in the late 1990's; replacing the gunhouse with a reduced Radar Cross Section assembly and replacing the hydraulic loading mechanism with an all electric system. This particular gun has been nicknamed the "Kryten Gun" by members of Royal Navy, after the odd shaped head of a robot from the British Sci-fi comedy series Red Dwarf.

155mm variant

The Ministry of Defence (MoD) is investigating a proposal from BAE Systems to "up gun" the 4.5 inch to accept the 155 mm gun barrel and breech from the AS-90 self propelled gun. This would introduce a common gun calibre with the British Army and Royal Navy, helping with ammunition logistics, and encouraging joint Army-Navy development of extended range and precision guided shells. A £4m contract has been awarded to develop a prototype, and firing trials are scheduled for 2009.