| Ordnance QF 4.5 inch gun Mk I, II, III, IV, V | |
| Origin: | United Kingdom |
| Type: | Naval gun Anti-aircraft gun |
| Is Ranged: | YES |
| Is Artillery: | YES |
| Is Uk: | YES |
| Used By: | British Commonwealth |
| Wars: | Second World War Korean War Falklands War |
| Number: | Navy: Army: 474 |
| Part Length: | Bore: 16feet 45 calibres |
| Cartridge: | Fixed or Separate QF 113 640–645 mm R[1] |
| Cartridge Weight: | 55lb× |
| Caliber: | 4.45adj=onNaNadj=on |
| Rate: | 12 RPM for Mk II BD mount. 16 RPM recorded for Mk III UD mount.[2] |
| Velocity: | 2449ft/s[3] |
| Max Range: | 20750yd at 2449ft/s AA:41000abbr=onNaNabbr=on |
| Breech: | Mks I - IV: Horizontal sliding block Mk V: Vertical sliding block |
| Elevation: | 0° to +80° |
| Traverse: | 360°[4] |
The QF 4.5 inch gun has been the standard medium-calibre naval gun used by the Royal Navy as a medium-range weapon capable of use against surface, aircraft and shore targets since 1938. This article covers the early 45-calibre family of guns up to the 1970s. For the later unrelated 55-calibre Royal Navy gun, see 4.5 inch Mark 8 naval gun. Like all British nominally 4.5 inch naval guns, the QF Mk I has an actual calibre of 4.45 inches (113 mm).[5] [6]
From the BL Mark I gun of 1916 the 4.7-inch (120 mm) calibre was the mid-calibre weapon of the Royal Navy, used particularly on destroyers. Apart from some ships armed with QF 4-inch Mk V guns due to shortages, it remained the standard weapon for destroyers up to the W-class destroyers of 1943. Its usefulness 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 in destroyer classes built prior to the introduction of the 4.7 inch twin mount (see HACS), and the setting of fuzes by hand on early, pre-war, mountings. Later 4.7 inch mountings used mechanical fuze setters that were identical to those used on the 4.5 inch mountings.[7]
The QF 4.5 inch L/45 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 had a heavier shell, resulting in a more powerful weapon.
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.
During the 1950s, a change was made in weapons systems nomenclature which focused on the gun mount rather than the gun. 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 Leopard-class frigates and County-class destroyers and three in the Daring-class destroyers. 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. The evolution of the 45-calibre 4.5 inch gun family ended with the Mark V gun / Mark 6 mounting. It has been replaced by a new weapon of original design, the 4.5 inch Mark 8 with a 55 calibre-long barrel.
Ships with 4.5 inch guns QF Mark I in twin mounting UD Mark III
Ships with 4.5 inch guns QF Mark III in twin mounting BD Mark II
Ships with 4.5 inch guns QF Mark III in twin mounting BD Mark II**
Ships with 4.5 inch guns QF Mark III in twin mounting BD Mark IV
Ships with 4.5 inch guns QF Mark IV in single mounting CP Mark V
Ships with 4.5 inch guns Mark 5* (rebuilt mounting CP Mark V).
Ships with 4.5 inch guns QF Mark V in twin mounting UD Mark VI (later renamed gun Mark 6)
QF Mark II was a single gun mounting (Mounting Mk 1) anti-aircraft gun in static sites. The pedestal mount was bolted to concrete in an unarmoured turret, a travelling platform was available to transport the gun and mounting between positions. The first unit became operational in February 1939. These 16.5 ton anti-aircraft mountings had a maximum elevation angle of 80 degrees. However, most mountings were Mark 1A with an elevation range of -9.5 to 80 degrees. This enabled the gun to be dual role (anti-aircraft and coastal defence) in coastal areas. Armour piercing rounds were provided for anti-ship engagements.
The guns were fitted with Magslip electrical data transfer from Predictors AA Nos 3, 5 and 10 and were probably used initially with GL radars and UB 10 18 feet base optical height and range finders. AA control radars evolved rapidly. The gun was laid and fuzes set by pointer matching, it is unclear the extent to which advances in 3.7-inch fire control were applied to 4.5-inch. During the war Machine Fuze Setter No 10 was added, This improved the rate of fire from 8 to 10 rounds per minute and raised the effective ceiling to 34,500 feet. Gun positions were usually in the vicinity of naval bases where they could use the naval ammunition supply. Initially the standard fuze was an igniferous design, No 199 with a maximum running time of 30 seconds that limited performance. Subsequently, No 209 a mechanical time fuze was introduced. It appears that VT fuzes were not issued. Guns were usually deployed in troops of 4 as part of a two-troop battery, although sections of two guns occupied some positions. Deployment included:
UK (Royal Artillery) June 1940:[9]
(the AA divisions included 3-inch and 3.7-inch regiments in addition to 4.5-inch)
Far East January 1942:[10]
Mediterranean June 1943:[11]
Middle East January 1943:[12]
West Africa Dec 1941:[13]
India Dec 1941:[14]
Colonel Probert of the Armaments Research Department developed rifling with tapered groove depth and with the last few inches of the barrel being smoothbore. This was used with a 4.5 barrel lined down to 3.7 inches but retaining the large chamber, allowing a large propelling charge to be employed. Ordnance, QF 3.7 inch Mk 6, only on a static mounting, entered service in 1943 and continued in service until 1959. It had an effective ceiling of 45,000 feet.[15] [16] The high performance of QF 3.7 inch Mk 6 and QF 5.25 inch meant that QF 4.5 inch was not retained in land service after World War II.
