4.5 inch (114 mm) gun

Encyclopedia : 4 : 45 : 45I : 4.5 inch (114 mm) gun

The BAE RO Defence 4.5 inch (110 mm) Mk 8 Mod 0 gun of HMS Grafton

The 4.5 inch (114 mm) gun has been the standard medium-calibre gun used by the Royal Navy as a medium range weapon capable of use against surface, aircraft and shore bombardment targets since 1938. The current 4.5 inch L/55 Mark 8 gun is manufactured by BAE Systems. All British 4.5 inch guns actually have a calibre of 4.45 inches (113 mm).

Contents

1 History
2 World War II variants
3 Post war variants
4 Use
5 See also

History

From the BL Mark I of 1916, the 4.7 inch gun (119 mm) was the mid-calibre weapon of choice for the Royal Navy, used particularly on destroyers. Apart from some ships armed with 4 inch guns due to supply problems, it remained the standard weapon for destroyers up to the W class destroyer of 1943. However, its usefullness as an anti-aircraft weapon had been limited by the failure to develop a mounting with elevation over 55°, the lack of a predictive fire control system (see article HACS) and the setting of fuzes by hand.

The QF 4.5 inch L/45 (114 mm) was developed originally as a dual-purpose weapon with which to arm aircraft carriers and reconstructed battleships and battlecruisers. It was later developed as a new dual-purpose weapon with which to arm destroyers, supplanting the ubiquitous 4.7 inch gun. Despite the lower calibre, it actually had a heavier shell, resulting in a more powerful weapon.

World War II variants

The nomenclature system for guns used by the Royal Navy can be somewhat confusing. The gun and mounting each have their own Mark number and a letter(s) giving additional information. QF stands for "quick firing", UD for "upper deck", BD for "between decks" and CP for "central pivot".

QF Mark I - adopted after failure of a 5" gun project and used a fixed round, which proved to be somewhat heavy for the loaders to keep up the intended firing rate. Was fitted in twin mountings UD Mark III.
QF Mark II - used by the British Army as an anti-aircraft gun, with the barrel lined down to 3.7 inches to use the same ammunition as existing weapons.
QF Mark III - same as Mark I, except for firing mechanism. Was fitted in twin mountings BD Mark II, BD Mark II** and BD Mark IV.
QF Mark IV - used a two part (charge and shell) ammunition system. Designed specifically for use by small warships. Fitted in mountings BD Mark IV, CP Mark V and UD Mark VI.
QF Mark V - a further development of the Mark IV, designed from the outset for anti-aircraft use with remote power control (RPC, where the guns automatically train and elevate the target) and a high rate-of-fire assisted by automatic ramming. Carried in the mounting UD Mark VI, with separate high-angle and low-angle hoists for the two types of ammunition (AA and SAP/HE) and a third for the cartridges

Some 800 naval 4.5" guns of various marks were built. Including the gunhouse, gunbay and magazine crew, a twin turret mounting required up to 30 men.

Post war variants

During the 1950s, a change was made in designating the weapons systems which focussed on the gun mount rather than the gun itself. Together with a change from Roman numerals, the Gun QF Mark V on mounting BD Mark VI became simply the Mark 6. The Mark 7 was never produced as the planned Malta class aircraft carriers they would have been used on were never built.

The majority of new escort vessels built for the Royal Navy in the 1950s and 1960s carried at least one Mark 6 mounting, with two in the Salisbury class frigate and County class destroyer and three in the Daring class destroyer. This gave these ships a level of firepower unprecedented only 15 years earlier. The Type 81 Tribal class frigates were an exception, using reconditioned Mark V mounts from scrapped C class destroyers that were fitted with RPC and known as the Mark 5* Mod 1.

A completely new type of 4.5 inch gun was designed in the 1970s for the Royal Navy's new classes of frigates and destroyers. The new weapons, built by Vickers, resemble the Italian OTO design and the outer shell of the mounting is built from fibreglass. The gun for the mount was developed by the Royal Armament Research and Development Corporation using the 105 mm gun-howitzer of the Abbot self-propelled gun as a starting point. The new weapon emphasised reliability over a high rate of fire, hence the decision to switch to a lighter, single barrel mount. The ammunition is also of a new one-piece design. The weapon is semi-automatic and therefore needs fewer people to operate. There is no one in the gunhouse, and only a few personnel are required in the gunbay to load the feed ring, in addition to the and the magazine crew. It has a rate of fire of about 20 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. It entered Royal Navy service on the new destroyer Bristol in 1973.