QF 4.7 inch Mark XI gun

The 4.7 inch QF Mark XI was a 120-mm 50-calibre naval gun deployed on Royal Navy (RN) and allied destroyers during World War II.

Country Name Origin Year
United Kingdom - UK (Great Britain) 1941
Country Name Operational Year Retirement Year
Turkey (Ottoman Empire) View
United Kingdom - UK (Great Britain) 1941 1970 View

The QF 4.7-inch Mk XI gun, on the Mk XX twin mounting, was introduced to the RN aboard the L and M class destroyers, in commission from 1941 onwards. It featured a 62 lb (28.1 kg) shell fired at 2538 ft/second (774 m/s) to a maximum range of 21,240 yards (19,420 m) at 45 degrees of elevation. The Mk XX mounting was fully enclosed, but the hoists did not revolve with the turret. The gun's firing cycle was six seconds and the separate shell and cordite hoists for each gun provided shells and cartridges at a rate of 10 per minute. The shells and cartridges were transferred from the hoists to the tilting tray of the fuze-setting machine by hand. Once the fuzes were set, they slid forward to the loading tray from which they were rammed forward into the breech by a hydraulic rammer. The horizontal sliding-block breech opened semi-automatically after the guns fired.

The guns could be loaded at any angle of elevation. The Mk XX mounting could elevate to a maximum of 50° and depress to -10°. The turret had a maximum powered training rate of 10° per second, but was manually elevated. Including the crew and ammunition, the revolving weight of the mounting was 37.363 long tons (37.963 t). It was protected by a gun shield .25 inches (6.4 mm) thick., too thin to hold a direct hit, but still appreciable versus small splinters, explosions, small caliber rifles.

With a shell 24% heavier, the new gun was far more powerful than the previous 45 calibre long 4.7 inch gun making it a match for a weapon such as the Italian 120/50 mm, whilst also improving the air defence role. It could now penetrate 3 inches (76.2 mm) of armour at a range of 10 km rather than 5.9 km. In the Battle of Pantelleria on 15 June 1942), HMS Marne and Matchless engaged a superior Italian task force. Marne fired 704 shells, Matchless 746, while HMS Ithuriel (with four 4.7 /45) managed to fire only 246. Marne hit with a single shell the cruiser RN Eugenio di Savoia at around 5.50 AM. Matchless failed to hit the other cruiser, RN Montecuccoli, but later hit the large destroyer Ugolino Vivaldi. The new 120/50 mm shell was heavy and powerful, and the Italian destroyer was soon laying dead in the water, with a furious fire at midship. That destroyer was saved only towing her to a near naval base, where the fire was finally extinguished.

In the worlds of Tony di Giuliano, the 120/50 Mark XI gun was the perhaps the finest destroyer gun made by British during the World War II, but it was also heavy and costly, as were the ships equipped with it. Wartime production required a much greater production of ships and guns, so cheaper weapons were installed in many other classes, like the 'O' and 'P' (102 mm) and furthers (with the old 120 mm), until the 114 mm (4.5 in) started to replaced them, as the first, powerful dual purpose destroyer gun.

Type Dual-purpose gun
Place of origin United Kingdom
Service history
In service 1941-1970
Used by Royal Navy
Turkish Navy
Wars World War II
Korean War
Production history
Designed 1937–39?
Number built 87
Specifications
Weight 3.351 long tons (3,405 kg)
Length 247.7 in (6.29 m)
Barrel length Bore: 236.2 in (6.00 m) L/50 (cal)
Shell Separate-loading
Shell weight 62 pounds (28.1 kg) SAP orHE
Calibre 4.7 inches (120 mm)
Breech Semi-automatic horizontal sliding-block
Recoil Hydro-pneumatic
Elevation -10° to +50°
Rate of fire 10 rounds per minute
Muzzle velocity 2,538 ft/s (774 m/s)
Maximum firing range 21,240 yards (19,420 m) at 45°

End notes