4.5"/45 (11.4 cm) QF Mark V
(Mark 6 and Mark 7)
Updated 27 October 2012

This gun was intended to correct the many deficiencies of British destroyer weapons of World War II and was extensively used on ships built after the war.  Unlike previous types, this weapon was designed from the outset for high elevations, automatic aiming (RPC) and a fast rate of fire.  The weapon had many novel features, notably a loading tray, with which the gun recoils, and a rammer, which is pushed clear of the gun's axis by the vertically closing breech block.  Ammunition was supplied by two magazines, each with a separate shell hoist, one for AA and one for HE/SAP.  A third hoist supplied the cartridges.

The ramming mechanism proved to be overly complex and prone to faults.  For this reason, the high rate of fire initially expected could not be realized in practice and most gun crews relied upon hand-loading in order to maintain a steady rate of fire.  Despite this problem, these guns proved to be reliable in service and gave a good account of themselves during the Falklands War.

Service introduction was on the Australian "Modified Battle" class destroyers Anzac and Tobruk.  In Britain, these weapons were first used on the Daring class destroyers, about which was said:  "At last the RN had a modern destroyer with a longitudinally framed, welded hull, efficient and compact machinery, AC electrics and an effective dual-purpose armament.  These 'innovations' were introduced a decade later than in the USN" - D.K. Brown RCNC.

Nomenclature note:  In the 1950s the British weapon designation system changed from being per the gun itself to being per the mounting the gun was used in.  At the same time, arabic numerals replaced roman numerals.  Some confusion was created under this new system because older weapons were redesignated, even though the weapons and mountings themselves did not change.  Under this new system, the combination of the "4.5-in Mark V gun" as used in the "Mark VI twin mounting" was redesignated as the "4.5-in Mark 6" gun mounting.  As could be expected, these changes have led to much confusion as to what weapons were actually used on any particular ship.  For this reason, at the top of this datapage I show both the original per-the-gun designation and, in parenthesis, the per-the-mounting redesignations.

The "Mark 7" was the never-built mounting intended for the Malta class carriers which would have used the same Mark V gun barrel as did the Mark 6 mounting.  It has been speculated that the Mark 7 mounting might also have been used on the Lion class battleships.

This weapon had a loose barrel construction.  The barrel was withdrawn to the rear and was held in place by retaining and locking plates attached to the breech ring.  The breech block moved vertically, opened hydraulically and closed by spring operated racks.  The breech ring was screwed and shrunk onto the jacket.  About 300 guns were manufactured.

All British 4.5" naval guns have an actual bore diameter of 4.45" (11.3 cm).


RAN Vampire
Photograph courtesy of the Australian National Maritime Museum


HMS Daring off Malta in December 1953
IWM Photograph


Chilean Frigate Almirante Condell (PFG-06) in 1999
U.S. Navy Photograph No. 990705-N-5862D-001

Images at The Vickers Photographic Archive

See 0751

Gun Characteristics
Designation 4.5"/45 (11.4 cm) QF Mark V
Ship Class Used On Britain
   Prototype installed on HMS Saintes
   Lion (1945), Malta, Daring, County, Leander, Leopard (Type 41), Whitby (Type 12) and Salisbury (Type 61AD) classes

   Modified Battle, Daring, and River (Type 12M/I) classes

   Almirante Condell class

   Van Speijk class

Date Of Design 1944
Date In Service 1947
Gun Weight 6,304 lbs. (2,859 kg) including breech mechanism
Gun Length oa 241.25 in (6.128 m)
Barrel Length 202.0 in (5.131 m)
Rifling Length 170.9 in (4.341 m)
Grooves (32) 0.037 in deep x 0.291 (0.94 x 7.39 mm)
Lands 0.1459 in (3.706 mm)
Twist Uniform RH 1 in 25
Chamber Volume 600 in3 (9.83 dm3)
Rate Of Fire Designed:  24 rounds per minute (power)
Service:  12 - 14 rounds per minute (hand)
Burst mode:  18 rounds per minute (hand)
Type Separate
Projectile Types and Weights HE - 55 lbs. (25 kg)
SAP - 55 lbs. (25 kg)
AA - 55 lbs. (25 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge 11.04 lbs. (5.0 kg) SC 122
13.63 lbs. (6.18 kg) NF/S 198-054
Brass Cartridge -  38.5 lbs. (18.6 kg) with SC charge
Muzzle Velocity New gun:  2,449 fps (746 mps)
Average gun:  2,350 fps (716 mps)
Working Pressure 20.5 tons/in2 (3,230 kg/cm2)
Approximate Barrel Life 650 rounds
Ammunition stowage per gun N/A
Note:  Projectiles were 5/10crh.
Elevation With 55 lbs. (25 kg) HE Shell
Range @ 45 degrees 20,750 yards (18,970 m)
AA Ceiling @ 80 degrees 41,000 feet (12,500 m)
Armor Penetration with 55 lbs. (25 kg) SAP Shell
NC Armor
Deck Armor
10,500 yards (9,600 m)
2.5" (76 mm)
Note:  Data from "British Battleships of World War Two."  Assumes a perpendicular impact.
Mount / Turret Data
(see Note 4)
Twin Mountings

   Daring (3), County (2), Leander (1), Type 12 (1), Type 41 (2) and Type 61AD (1):  RP 41 Mark VI
   Lion (1945) (6 - 8) and Malta (8):  RP 41 Mark VII

   Modified Battle (2), Daring (3) and Type 12M/I (1):  RP 41 Mark VI

   Almirante Condell (1):  RP 41 Mark VI

   Van Speijk (1):  RP 41 Mark VI

Weight  Mark VI:  98,560 lbs. (44,706 kg)
Mark VII:  N/A
Elevation -15 / +80 degrees
Elevation Rate 25 degrees per second
Train about +150 / -150 degrees
Train Rate 25 degrees per second
Gun recoil N/A

1) Welding was extensively used for the first time in British gun-mount construction.  The mountings were unusual in that the training mass was entirely supported by a cantilevered structure that provided a circular gunbay clear of obstructions which thus allowed for easier transfer of ammunition to the revolving structure.  This design did, however, greatly increase the structural weight needed to support the mounting.

2) These mountings used hydraulic rams for elevation.

3) The RP 41 Mark VI was a true turret with three upper and three lower hoists per gun, one for AA rounds, one for other projectiles and one for cartridges.

4) The design of the last version of the Lion class battleships was never finalized and the make up of their secondary armament is somewhat of a speculative nature.

5) The gun axes were about 38 in (96.5 cm) apart.

Data from
"Nelson to Vanguard:  Warship Design and Development 1923-1945" by D.K. Brown
"Warship Pictorial:  The Building of HMS Duke of York" article by Ian Buxton in "Warship Volume VIII"
"Naval Weapons of World War Two" and "British Naval Guns 1880-1945 No 16" article in "Warship Volume IX" both by John Campbell
"The Naval Institute Guide to World Naval Weapon Systems 1991/92" by Norman Friedman
"Vanguard to Trident:  British Naval Policy since World War Two" by Eric Grove
"Warships of World War II" by H.T. Lenton and J.J. Colledge
"British Battleships of World War Two" by Alan Raven and John Roberts
Page History

03 November 2008 - Benchmark
07 August 2010 - Corrected number of mountings on Type 41 Frigates
12 February 2012 - Updated to latest template
27 October 2012 - Added details on Australian ships