9.2"/47 (23.4 cm) Mark X
Updated 06 December 2015

This gun was extensively used by both the Army and the Navy.  Naval guns were the secondary armament on pre-dreadnought battleships and the main guns on armored cruisers.  Some of these guns were later transferred to the Army after the ships were scrapped while others were reused on monitors built during World War I.  The Army version was the standard coastal defense gun until well after the end of World War II.  When Britain and Canada gave up their coastal defense artillery in 1956, a quantity were then sold to Portugal and Turkey where some of them may still remain.

Extracts from Admiral E.C. Troubridge's courtmartial regarding these guns include these comments:  "The 9.2-inch Mark XI [guns used on HMS Defence] has always been known as an inaccurate gun.  It is probably due to the high muzzle velocity.  The 9.2-inch Mark X [guns]. . . are inaccurate at certain stages of wear of the gun.  Otherwise they are accurate guns" and "For the 9.2-inch Mark X and XI and 7.5-inch Mark II the average spread [dispersion] was 200 - 250 yards at a range of 7000 - 8000 yards" (180 - 230 m spread at ranges of 6,400 - 7,300 m).

Of built-up construction and wire-wound.  Suffered from "steel choke" and too large a propellant grain.  In Army guns a smaller grain propellant was eventually adopted and a tapered inner "A" tube was gradually introduced, thus bringing them up to modern standards.  A total of 112 guns were made for the Navy of which 12 were later transferred to land service and a further 170 guns were built for the Army.  Actual bore length of all guns was 46.66 calibers.

The prefix "A" is sometimes found and indicates guns with a "pure couple" breech mechanism rather than the standard three-motion breech mechanism.  Mark Xx designation covers guns with tapered inner "A" tubes.  The suffix RT following Mark X or Mark Xx indicated a modification to fit World War II railway mountings, but it is believed that no guns were so altered.  Two guns intended for the reconstructed Turkish ship Messudieh but never delivered were designated as XT.  This weapon was to have used smaller propellant charges with a resulting reduction of 200 fps (61 mps) in the muzzle velocity, but could take the standard MD37 charge.  The XT guns had Elswick three-motion short arm breech mechanisms and the British kept these as special reserve railway guns.  The designation Mark Xv covers two Army guns that were wire-wound over only part of their length and with no "B" tube.


HMS Natal with bow and stern 9.2"/47 (23.4 cm) single guns
Photograph from Allan C. Green collection of glass negatives
State Library of Victoria Image H91.325/2121

Click here for additional pictures
Gun Characteristics
Designation 9.2"/47 (23.4 cm) Mark X
Ship Class Used On King Edward VII, Drake, Cressy, Duke of Edinburgh and Warrior Classes
Monitors M15, M16, M17 and M18
Date Of Design about 1895
Date In Service 1900
Gun Weight 28.313 tons (28.67 kg) including breech mechanism
Gun Length oa 442.4 in (11.237 m)
Bore Length 429.3 in (10.950 m)
Rifling Length 353.8 in (8.987 m)
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume 8,123 in3 (133.1 dm3)
Rate Of Fire
(see Notes 2 and 3)
3 - 4 rounds per minute

1) The prefix "A" is sometimes found and indicates the use of a "pure couple" breech mechanism.

2) The Rate of Fire figure given above is found in references, but "Warrior to Dreadnought:  Warship Development, 1860-1905" quotes Jellicoe's 1906 figures for rates of fire for these guns in gunlayers' tests and in battle practice and notes that the latter figures corresponded well to those actually attained by the Japanese at Tsushima:

Gunlayers Test:  5 rounds per minute
Battle Practice:  2 rounds per minute

3) When used in monitors, the ROF is quoted at 1 round per minute.  Most coastal guns also had a ROF of about 1 round per minute.

4) Danger space for this gun against a 30 foot (9 m) target was estimated as follows:
   75 yards at   8,000 yards (69 m at   7,300 m)
   30 yards at 12,000 yards (27 m at 10,970 m)
     0 yards at 16,000 yards (  0 m at 14,630 m)

5) The monitors used spare guns and mountings originally intended for regunning Drake class cruisers.

Type Bag
Projectile Types and Weights APC 2crh - 380 lbs. (172.4 kg)
CPC 2crh - 380 lbs. (172.4 kg)
HE 4crh - 380 lbs. (172.4 kg)
HE 5/10crh - 391 lbs. (177.4 kg)
Bursting Charge APC - 12.9 lbs. (5.9 kg)
CPC - 35.4 lbs. (16.1 kg)
HE 4crh - 33.0 lbs. (15.0 kg)
Projectile Length APC - N/A
CPC - 35.4 in (89.9 cm)
HE 4crh - 32.1 in (81.5 cm)
Propellant Charge
(see Note 1)
World War I
   120 lbs. (54.4 kg) MD37
   107 lbs. (48.5 kg) MD26

World War II
   Standard charge:  109 lbs. (49.4 kg) SC150
   Super charge:  123.6 lbs. (56.1 kg) SC205

Muzzle Velocity MD37:  2,778 fps (847 mps)
MD26:  2,748 fps (838 mps)

Standard charge:  2,748 fps (838 mps)
Super charge:  2,872 fps (875 mps)

Working Pressure N/A
Approximate Barrel Life 450 rounds
Ammunition stowage per gun King Edward VII:  150 rounds
M15:  120 rounds
Others:  N/A

1) MD charges were used prior to and during World War I while standard and super charges were used by coastal batteries during World War II.

2) Original shells were all 2crh.  During World War I, 4crh projectiles were developed for the monitors.  Coastal artillery was supplied with 5/10crh shells during World War II.

3) The following comments are by Nathan Okun:

The British Coast Defense Gun 9.2" APC shell weighed 380 lb and had a 3.4% filler (12.9 lb) for all versions made during World War I and World War II.  The last version, the 9.2" Mark XIIA APC, had two versions, one made in Britain and one made in the US during World War II by Crucible Steel Company.  The US version was identical to the British version as to the body shape, base plug, weight, and windscreen, but the nose of the shell was the US Navy early World War II very blunt point and it used a US-style early World War II AP cap and, I believe, the US Sheath Hardening Pattern, not the British more deformable World War II APC hardness pattern.  Under test the US design satisfied all ballistic test specifications, though the base plug was exposed more by base slap breakage at oblique impact as it penetrated than the British softer lower body was.  The British cup-shaped Patent Relief Base Plug worked though and both the US and British designs were still effective ("fit to burst") after penetrating the armor. 

The post-World War I designs all used Shellite fillers, though those during World War I were much like their contemporaries and used Lyddite prior to 1918 and Shellite afterwards (there was a Greenboy version of this projectile, too).

I would have thought that with this large cavity, which was exactly the same as in World War I, the 9.2" Mark XIIA APC would have had problems with projectile breakup against thick armor at moderate obliquity (circa 1-caliber-thick plate at around 30 degrees obliquity).  However, this was not the case.  In fact, these projectiles -- both the US and British designs -- are, from the tests I have seen, THE BEST BRITISH APC PROJECTILES EVER MADE!!  They penetrate armor better and remain in one piece under more extreme impact conditions (I even gave them a separate entry in FACEHARD's British projectile table).  I have no idea why they were so good.  Obviously there are "sweet spots" for every kind of mechanical design and this shell happens to be right on top of one.

Elevation With 380 lbs. (172.4 kg) 2crh CPC Shell
15 degrees 15,500 yards (14,170 m)
@ 2,778 fps (847 mps)
30 degrees 22,000 yards (20,120 m)
Elevation With 380 lbs. (172.4 kg) 4crh HE Shell
30 degrees 25,700 yards (23,500 m)
@ 2,778 fps (847 mps)
Elevation With 391 lbs. (177.4 kg) 5/10crh HE Shell
35 degrees
Coastal Artillery with standard charges
29,200 yards (26,700 m)
@ 2,748 fps (838 mps)
35 degrees
Coastal Artillery with super charges
(see Note 2)
about 32,600 yards (29,810 m)
@ 2,872 fps (875 mps)
35 degrees
Coastal Artillery with super charges
(see Note 2)
36,700 yards (33,560 m)
@ 2,872 fps (875 mps)

1) The gun mounting manual for this weapon says that the gunsights were calibrated up to 14,000 yards (12,800 m) which was for a 15 degree elevation and a muzzle velocity of 2,643 fps (806 mps).

2) The first supercharge figure is from "Naval Weapons of World War Two" while the other is from "The Naval Institute Guide to World Naval Weapon Systems 1991/92."  This may reflect the performance of different shell types.

3) As built, naval mountings were only able to elevate to +15 degrees.  Mountings later fitted to the monitors were modified to allow +30 degrees maximum elevation.  See Mount / Turret notes, below.

Armor Penetration with 380 lbs. (172.4 kg) 2crh AP Shells
Range Vertical Steel Plate
3,000 yards (2,740 m) 14 in (35.6 cm)
4,550 yards (4,160 m) 9.2 in (23.4 cm)
Note:  These figures are from "British Battleships:  1860 to 1950" and are for a muzzle velocity of 2,751 fps (839 mps).
Range Vertical KC Plate
3,000 yards (2,740 m) 9.7 in (24.6 cm)
6,000 yards (5,480 m) 7.7 in (19.6 cm)
9,000 yards (8,230 m) 5.3 in (13.5 cm)
Note:  These figures are from "The Grand Fleet:  Warship Design and Development 1906-1922" and assume a 90 degree inclination.  These trials were conducted with salt-filled (blind) shells and almost certainly overstate the performance of British shells of the early twentieth century.
Armor Penetration with 380 lbs. (172.4 kg) CPC Projectile
Range Vertical KC Plate
3,000 yards (2,740 m) 6.5 in (16.5 cm)
Note:  Data from "The Grand Fleet:  Warship Design and Development 1906-1922" for an angle of obliquity of 30 degrees and a striking velocity of 1,826 fps (557 mps).  Projectiles were salt-filled (blind).
Mount / Turret Data
Designation Single mounts
  Early Cressy class (2) and Drake (2):  Mark V
  King Edward VII (4), Duke of Edinburgh (6) and Warrior (6) classes:  Mark VS
  Later Cressy class (2):  Mark VI

  Monitors (1):  Mark V (modified)

(see Note 1)
Mark V:  110 tons (112 mt)
Others:  N/A
(see Note 2)
Naval Mountings:  -5 / +15 degrees

Reworked Monitor Mountings:  -5 / +30 degrees

Army Coastal Artillery: -5 / +15, +30 or +35 degrees

Elevation Rate N/A
Train Pre-dreadnoughts:  about +60 / -60 degrees
Armored Cruisers - end guns:  +142 / -142 degrees
Armored Cruisers - beam guns:  +60 / -60 degrees
Train Rate N/A
Gun recoil N/A
Loading Angle N/A

1) Four spare Mark V mountings were reworked for the monitors by having their armor replaced with thin sheet steel and the rear of the shield removed entirely in order to reduce weight.  Hydraulic machinery was also removed for the same reason and these mountings thus became completely hand worked.  These changes reduced the total revolving weight by about 40 tons (41 mt).

2) HMS Commonwealth and HMS Zealandia (King Edward VII class) and the monitors had their mountings modified to give +30 degrees maximum elevation.

3) Early in 1917 three Mark VS mountings altered to give +45 degree elevation were installed on the Belgian coast.

4) Mark V mountings were built by Elswick while Mark VI mountings were built by Vickers.

Data from
"Warrior to Dreadnought:  Warship Development 1860-1905" and "The Grand Fleet:  Warship Design and Development 1906-1922" both 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 7" article in "Warship Volume VI" both by John Campbell
"The Naval Institute Guide to World Naval Weapon Systems 1991/92" by Norman Friedman
“Policy and Operations in the Mediterranean 1912-14” by E.W.R. Lumby
"Cruisers of the Royal and Commonwealth Navies" by Douglas Morris
"British Battleships:  1860 to 1950" by Oscar Parkes
"A Concentrated Effort:  Royal Navy Gunnery Exercises at the End of the Great War" article by William Schleihauf in "Warship International" No. 2, 1998
Special help from Daniel Muir, Nathan Okun and Dave Alton
Page History

09 November 2008 - Benchmark
22 February 2009 - Added information about monitors
16 June 2012 - Added picture of HMS Natal
05 January 2014 - Added additional pictures datapage
06 December 2015 - Moved Vickers Photograph Archive links to additional pictures page