4.5 inch (114 mm) Mark 8 naval gun

4.5 inch Mark 8 naval gun
4.5 inch Mk 8 Mod 1 naval gun on HMS Defender. The multi-faced gunhouse is designed to reduce radar cross section.
Type	Naval gun
Place of origin	United Kingdom
Service history
In service	1972 - present
Wars	Falklands War Invasion of Iraq 2003 2011 military intervention in Libya
Production history
Designer	Mod 0 : Royal Armament Research and Development Establishment Mod 1 : Royal Ordnance Defence
Variants	Mod 0, Mod 1
Specifications
Barrel length	244.75 inches (6.217 m) bore (55 calibres)
Shell	Fixed QF 46 pounds (21 kg) HE
Calibre	4.45-inch (113 mm)
Maximum firing range	27.5 kilometres (30,100 yd)

The 4.5 inch Mark 8 is a British naval gun system which currently equips the Royal Navy's destroyers and frigates, and some British destroyers and frigates sold to other countries.

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 55-calibre Mark 8 gun replaced the World War II era 45-calibre QF 4.5 inch Mk I - V naval guns. Like all British 4.5 inch naval guns, it has a calibre of 4.45 inches (113 mm).

A completely new type of 4.5 inch gun with a longer 55-calibre barrel, it was designed in the 1960s for the Royal Navy's new classes of frigates and destroyers. The new weapon, built by Vickers Ltd Armament Division, was developed by the Royal Armament Research and Development Establishment using the Ordnance, QF 105 mm L13 of the Abbot self-propelled gun as a starting point (it used electrical primers). The outer shell of the gunhouse is built from glass-reinforced plastic (GRP).

The new weapon emphasised reliability and rapid response to fire first round from shutdown state (particularly for defence against missiles) 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 and can be operated by a smaller crew than its predecessors. With no personnel in the gunhouse, loading is supported by personnel in the gunbay to load the feed ring and in the deep-magazine to pass ammunition to the gunbay. The captain of the gun in the control room ensures continued weapon readiness and the gun controller in the operations room aims and fires the weapon. The gun has a rate of fire of about 25 rounds per minute and a range of 12 nm (22 km; 27.5 km with the newer High Explosive Extended Range round).