4"/45 (10.2 cm) QF HA Marks XVI, XVII, XVIII and XXI
Updated 20 January 2013

Intended for use as a DP weapon, the Mark XVI was a reasonably good AAA gun although many considered it as being too small for the anti-ship role.  This weapon superseded the 4"/45 (10.2 cm) Mark V HA gun on new cruiser construction in the 1930s.  In addition, many older cruisers and capital ships had their Mark V guns replaced with these more powerful weapons during refits.  A popular weapon, production could not keep up with demand until late in the war, resulting in many ships being armed with older weapons.

HMS Carlisle, a converted AA cruiser armed with these guns, shot down 11 aircraft during the war, the highest score among British cruisers.  The Auxiliary AA ship Alynbank, also armed with these guns, shot down six aircraft.

These guns were noteworthy as having "neither long barrel life nor particularly high accuracy" - John Campbell.  This was blamed on the use of projectiles with a too-short parallel section which led to poor centering at the muzzle.

The Mark XVII was designed for some "County" class cruisers with the intention of replacing two of their single 4"/45 (10.2 cm) Mark V mountings with twin mountings without exceeding the Treaty weight limits.  This hair-splitting exercise was described as "ridiculous punctiliousness" by John Campbell.  Twelve guns were manufactured, all of which were later converted back to the Mark XVI standard.  The Mark XVIII was the original designation for an improved version of the Mark XVI but this was redesignated as the Mark XVI* before being accepted into service.  The Mark XXI was a lighter version built to revised design rules with an autofretted monobloc barrel and removable breech ring.

The original Mark XVI had an A tube, jacket from muzzle to removable breech ring and used a down-sliding breech block which was manually operated but opened semi-automatically.  The Mark XVI* was the most produced version and differed by having the A tube replaced by an autofretted loose barrel with a sealing collar at the front of the jacket.  Mark XVI guns when repaired were converted to the Mark XVI* standard.

Some 2,555 Mark XVI and XVI* along with 238 Mark XXI guns were manufactured in Britain.  Canada produced 504 Mark XVI* and 135 Mark XXI guns.  Australia produced a further 45 Mark XVI* guns.


4"/45 (10.2 cm) Mark XVI guns in twin Mark XIX mounting
Photograph copyrighted by the Naval Museum of Alberta, Canada and used here by their kind permission

Click here for additional pictures
Gun Characteristics
Designation 4"/45 (10.2 cm) QF HA Mark XVI, XVI*, Mark XVII and Mark XXI
Ship Class Used On Mark XVI and XVI*
   Many capital ships, a few aircraft carriers, most 8 inch (20.3 cm) and 6 inch (15.2 cm) cruisers
   AA Cruisers as rearmed, Abdiel minelayers, "Tribal", "Hunt" and "Weapon" class destroyers
   "L" class destroyers Lance, Gurkha, Legion and Lively
   "P" class destroyer Petard
   Australian and Canadian "River" class frigates
   Australian warships Parramatta, Warrego, Bathurst and Kanimbla
   Most sloops, auxiliary AA ships, AMCs, some landing ships, depot ships and netlayers 1938 - 1948

   Poland:  Destroyer Blyskawica

Mark XXI
   Loch Veyatie

Date Of Design About 1934
Date In Service 1936
Gun Weight Mark XVI:  4,495 lbs. (2,039 kg)
Mark XVI*:  4,502 lbs. (2,042 kg)
Mark XXI:  3,397 lbs. (1,541 kg)
Gun Length oa 190.5 in (4.839 m)
Bore Length 180.0 in (4.572 m)
Rifling Length 149.5 in (3.798 m)
Grooves (32) 0.037 in deep x 0.270 (0.94 x 6.86 mm)
Lands 0.1227 in (3.117 mm)
Twist Uniform RH 1 in 30
Chamber Volume 511.8 in3 (8.387 dm3)
Rate Of Fire 15 - 20 rounds per minute
Type Fixed
Weight of Complete Round HE - 63.5 lbs. (28.8 kg)
SAP - 66.75 lbs. (30.28 kg)
Projectile Types and Weights HE - 35 lbs. (15.88 kg)
SAP - 38.25 lbs. (17.35 kg)
Bursting Charge N/A
Projectile Length N/A
Complete round was 45.13 in (114.6 cm)
Propellant Charge Standard Charge:  9.0 lbs. SC 103 or 10.5 lbs. NF/S (4.09 or 4.8 kg)
Reduced Charge:  5.1 lbs. SC 061 (2.3 kg)

Cartridge - 28.5 lbs. (12.9 kg)

Muzzle Velocity Standard Charge:  2,660 fps (811 mps)
Reduced Charge:  2,000 fps (610 mps)
Working Pressure 20.5 tons/in2 (3,230 kg/cm2)
Approximate Barrel Life 600 rounds
Magazine capacity per gun
(see Notes 3 and 4)
Hood, Barham, Malaya and Warspite:  250 to 280 rounds plus 250 total star shells
Most Cruisers:  200 rounds
Edinburgh:  250 rounds
Roberts:  400 rounds

1) The sources below differ as to the muzzle velocity and range of these weapons.  I have chosen to use those given in "Naval Weapons of World War Two."

2) Outfits included SAP, HE, shrapnel and star shells.

3) Outfit on Edinburgh per gun was 250 HE, 65 practice HA, 4 practice LA, 4 Target smoke and 12.5 starshells.

4) Outfit on Roberts per gun was 80 SAP, 320 HE, 12 star and 83 practice.

Elevation With 35 lbs. (15.9 kg) HE Shell
Range @ 45 degrees 19,850 yards (18,150 m)
AA Range @ 80 degrees 39,000 feet (11,890 m)
Mount / Turret Data
(see Note 1)
Twin HA/LA Mount - Mark XIX

   Capital Ships:  Barham (4), Malaya (4), Warspite (4), Royal Sovereign class (4), Hood (7)
   Monitors:  Roberts class (4)
   Carriers:  Furious (6), Unicorn (4), Activity (1), Campania (2), Nairana (2), Vindex (2), Pretoria Castle (2)
   County Cruisers:  Kent class (4) except Suffolk (2) and Canberra (0), London class (4), Norfolk class (4), Exeter (2)
   Small Cruisers:  Leander class (4), Perth (4), Hobart (4), Arethusa class (4)
   Town Cruisers:  Southampton class (4), Edinburgh class (6)
   Colony Cruisers:  Fiji class (4), Ceylon class (4), Swiftsure class (4)
   Old Cruisers:  Danae (1), Dragon (1? - see Note 1)
   AA Cruisers:  Cairo (4), Calcutta (4), Carlisle (4), Curacoa (4), Caledon (3), Colombo (3)
   Cruiser/Minelayers:  Abdiel class - First Group (3) as rearmed; Abdiel class - Second Group (2) as built
   Destroyers:  "Tribals" (1), "P" class Petard (2), "L" class Lance (4), Gurkha (4), Legion (4) and Lively (4)
   Destroyers:  Canadian "Tribals" Cayuga (4), Athabaskan (4)
   Post-war Destroyers:  "Weapon" class (3)
   Old Destroyers:  Wallace (2), some "V" class (2) and "W" class (2)
   Escort Destroyers:  Hunt Type I (2), Hunt Type II (3), Hunt Type III (2), Hunt Type IV (3)
   Frigates:  "Bay" class (2), Canadian "River" class (1), Late Australian "River" Class (2)
   Sloops:  Fleetwood (1), Egret class (4), Black Swan class (3), Australian Parramatta (1)
   AMC:  Canton (2), Corfu (2)
   Sea-going Auxiliary AA ships:  Alynbank (4), Springbank (4), Foylebank (4), Palomares (3), Pozarica (4)
   Sea-going Auxiliary AA ships:  Tynwald (3), Ulster Queen (3), Canadian Prince Robert (5)
   LSH (L):  Bulolo (2), Lothian (2)
   LSI (L):  Glenearn (3), Glengyle (3), Glenroy (3)
   LSI (M):  Prince David (1), Prince Henry (1)
   Submarine Depot Ships:  Bonaventure (1), Montclare (2), Wolfe (2)
   Netlayers:  Guardian (1), Protector (1)

   Polish Blyskawica (4)

Single HA/LA Mounts

   Australian Parramatta (3) Warrego (3), Bathurst class (1), Kanimbla (1):  Mark XX
   Early Australian "River" class frigates (2):  Mark XX
   Loch Veyatie (1):  Mark XXIV

Weight Mark XIX:  37,072 lbs. (16,816 kg)
Mark XIX*:  About 39,300 lbs. (17,826 kg)
Mark XIX+:  About 36,000 lbs. (16,333 kg)
Mark XX:  22,064 lbs. (10,008 kg)
Mark XXIV:  19,039 lbs. (8,636 kg)
Elevation All:  -10 / +80 degrees
Elevation Rate
(see Note 2)
Manually operated, only

Units adapted for RPC:  15 - 20 degrees per second

Train 340 degrees
Train Rate
(see Note 2)
Manually operated, only 

Units adapted for RPC:  15 - 20 degrees per second

Gun recoil
(see Note 7)
15 in (38 cm)

1) Many older battleships and cruisers traded their single 4" (10.2 cm) Mark V guns for these twin mountings during the 1930s and early 1940s.  HMS Hood had four twin mountings added in 1937 and three more twin mountings added in 1940, at which time all of her 5.5" (14 cm) single mountings were removed.  British "Tribal" class destroyers had their "X" position 4.7" (12 cm) twin mounting replaced with one 4" (10.2 cm) twin mounting.  The first Abdiel group had their three 4.7"/45 (12.7 cm) Mark CPXIX twin mountings replaced by three 4" (10.2 cm) twin mountings.  The Hunt Type I destroyers were originally intended to mount three twin mountings, but an error in stability calculations resulted in the removal of "X" mounting.  Petard was originally armed with four 4" (10.2 cm) Mark V guns in single mountings, she was rearmed with two 4" (10.2 cm) twin mountings during the war.  The post-war "Weapon" class destroyers had three twin mountings as completed, although one was later removed in order to add Squid ASW.  "Naval Weapons of World War Two" says that the cruiser HMS Dragon carried at least one Mark XIX mounting, but I can find no other reference that supports this claim.  HMS Belfast had two Mark XIX twin mountings removed in 1944-45 as weight compensation for growth in other areas.   Palomares and Ulster Queen had their three Mark XIX twin mountings replaced by three single 6" (15.2 cm) guns (type unknown) during the war.  The Polish destroyer Blyskawica had her 120 mm guns replaced in 1941 with these guns.  In the 1950s, the British guns were removed and she was then rearmed with Russian 100 mm guns.

2) The Mark XX single mounting was used only on Australian ships.  The Mark XXI gun in the Mark XXIV single mounting was a late-war development intended for "Loch" class frigates and "Castle" class corvettes but only Loch Veyatie, completed after the war, actually carried this gun and mounting.

3) As built, all twin mountings were manually operated.  Some were fitted with RPC during the war, there being three Metadyne types, RP 50, RP 51 and RP 52.  All three had the elevating and training motors on the mountings and drove the mounting through worm gears.  RP 50 and RP 52 had the Metadyne sets on the fixed structure while RP 51 had them on the rotating mass.  RP 50 had elevating and training rates of 15 degrees per second while the others had elevating and training rates of 20 degrees per second.  RP 51 and RP 52 had a joystick for local control.

4) The Edinburgh class cruisers had an unusual design feature in that their 4" (10.2 cm) guns were positioned well back from the secondary magazines, which were located under the flight deck.  To transport the ammunition from the magazine hoists back to the guns, these ships were equipped with a 110 foot (33.5 m) conveyer system which consisted of trolleys on a sort of railway, which "British Cruisers of World War Two" describes as being "a complicated arrangement which in action could easily be disrupted."

5) The gun axes were 21 in (53.3 cm) apart on the Twin Mark XIX.

6) The Twin Mark XIX mounting had three variations.  The standard Mark XIX had a relatively short shield which left the loaders exposed to shell fragments; the Mark XIX* which had an extended shield and was used on ships with off-mount blast structures; and the Mark XIX+ which did not have fuze setting machines.

7) The recoil distance given above is the nominal figure.  The absolute, metal-to-metal recoil distance was 16.5 in (42 cm).

Data from
"The Design and Construction of British Warships 1939-1945 Vol.1 - Major Surface Warships" by D.K. Brown
Big Gun Monitors:  The History of the Design, Construction and Operation of the Royal Navy's Monitors" by Ian Buxton
"Naval Weapons of World War Two" and "British Naval Guns 1880-1945 No 18" article in "Warship Volume X" both by John Campbell
"The Hunts" by John English
"British Carrier Aviation:  The Evolution of the Ships and their Aircraft" by Norman Friedman
"Destroyer Weapons of World War 2" by Peter Hodges and Norman Friedman
"Warships of World War II" by H.T. Lenton and J.J. Colledge
"Cruisers of the Royal and Commonwealth Navies" by Douglas Morris
"British Battleships of World War Two" and "British Cruisers of World War Two" both by Alan Raven and John Roberts
"Anatomy of the Ship:  The Battlecruiser Hood" by John Roberts
"Handbook for the 4 Inch Q.F. Mark XVI* Gun on the H.A. Twin Mark XIX and Single Mark XX Mountings" BR 257 1941

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28 October 2007 - Benchmark
24 September 2011 - Added Edinburgh ammunition outfit
16 June 2012 - Added picture of HMAS Barwon
20 January 2013 - Added additional picture page