The lack of a DP function for these weapons was keenly felt throughout the war as more British destroyers were sunk by air attack than from any other cause. What little AA capability that these weapons did have was hindered by a lack of a tachymetric (predictive) fire control system and the setting of HE time fuzes by hand. The last single mounting designed, the CPXXII, had a spring operated rammer, but all other single mountings were completely hand worked. The twin mounting had power ramming and used power training and elevation but no RPC gear was installed.
Mark IX was constructed of A tube, jacket 80 inches (203 cm) to the muzzle and breech ring. Used a manually operated horizontal sliding breech block with semi-automatic opening. Mark IXA was of loose barrel construction with a removable breech ring. Mark IX* denoted differences in breech ring and semi-automatic breech, which were originally used for two-part wire wound experimental guns. A number of Mark IX* guns were used on destroyers built for Argentina, Brazil and Turkey, but not all of these were delivered. Mark IX** denoted differences in breech ring for CPXVIII mounting. Mark IX**A was for guns converted to loose barrel construction with a removable breech ring. Mark IX**B were new loose barrel guns which differed from Mark IX**A in the breech ring/jacket connection and removable breech ring.
Mark XII was generally similar to Mark IX except that it had a removable breech ring. Mark XIIx had no register on the rear of A tube and breech rings were machined to match. Mark XIIB was of loose barrel construction.
A similar weapon was the Vickers 4.7"/45 (12 cm) "E" gun. This was an earlier design and differed from the Mark IX in that the "E" guns were wire wound for part of their length, had slightly different chamber dimensions and in having an inner A tube with only 28 rifling grooves. "E" guns were built solely for export and were not used on British warships.
A total of 742 Mark IX and 372 Mark XII guns were manufactured, including all variants. Mark IX**B was one of the largest volume variants, with 183 being made.
Actual bore diameter of all British 4.7" guns was 4.724" (12 cm).
The data that follows is specifically for the Mark IX and Mark XII guns except where noted.
4.7"/45 (12 cm) Mark IX gun in CPXVIII
mounting under construction at Vickers. Note the cartridge in the
loading tray. The net at the back of the gun was to slow the ejected
cartridge casing. The workman on the left appears to be setting a
time fuze but he actually has a dummy projectile.
(see Note 1)
|4.7"/45 (12 cm) QF Mark IX
4.7"/45 (12 cm) QF Mark XII
4.7"/45 (12 cm) Vickers "E"
|Ship Class Used On
(see Note 4)
Prototype mounted on Mackay
Argentina: Buenos Aires class (G class)
Turkey: Destroyers Demirhisar
and Sultanhisar (I class)
Prototype mounted on Hereward
Argentina: Mendoza destroyer class
Chile: Serrano destroyer
|Date Of Design||about 1928|
|Date In Service||1930|
|Gun Weight||Mark IX: 2.963 - 2.984 tons (3,011
- 3,032 kg)
Mark XII: 3.238 - 3.245 tons (3,290 - 3,297 kg)
|Gun Length oa||Mark IX: 220.62 in (5.604 m)
Mark XII: 224.08 in (5.692 m)
|Bore Length||212.6 in (5.400 m)|
|Rifling Length||179.3 in (4.552 m)|
|Grooves||(38) 0.037 in deep x 0.270 (0.94 x 6.86 mm)|
|Lands||0.1205 in (3.061 mm)|
|Twist||Uniform RH 1 in 30|
|Chamber Volume||Mark IX and Mark XII: 628 in3
Vickers "E": N/A
|Rate Of Fire
(see Notes 2 and 3)
|CPXXII (single) Mounting: 10 - 12
rounds per minute
CPXIX (twin) Mounting: 10 - 12 rounds per minute
Other Mountings: 7 - 10 rounds per minute
1) Prefixes to the RN gun designations were: C - percussion firing only; D - EMF and percussion; F - EMF (later type breech block); G - DEF and percussion.
2) CPXXII had spring powered rammers, all other single mountings were manually rammed. The CPXIX twin mounting had powered ramming. See "Mount / Turret Data" notes below for additional details.
3) As these were all open mountings, bad weather conditions such as experienced by many of these ships on Arctic convoy duty during World War II greatly reduced the ROF figures given above.
4) Use of Mark IX and XII by other nations: Seven modified "G" class destroyers were delivered to Argentina in 1938. At the start of the war in 1939, six "H" class destroyers were under construction for Brazil and four "I" class destroyers were under construction for Turkey. Turkey took possession of two of her destroyers in 1942, but the other eight warships were requisitioned by the Royal Navy. Two "N" class destroyers (ex-RN Noble (i) and ex-RN Nonpareil) were turned over the the Royal Netherlands Navy in 1942 and became RNN Van Galen (ii) and RNN Tjerk Hiddes.
|Projectile Types and Weights
(see Note 3)
|HE - 50 lbs. (22.68 kg)
SAP - 50 lbs. (22.68 kg)
|Bursting Charge||N/A - TNT|
|Projectile Length||HE - N/A
SAP - about 15 in (38 cm)
|Cartridge Case Type, Size and Empty Weight||Brass, 4.724 x 30.922 in (120 x 785.42 mm), N/A|
|Propellant Charge||11.58 lbs. (5.25 kg) SC 109
13.13 lbs. (5.96 kg) NF/S 164-048
Cartridge - 30.5 lbs. (13.8 kg) with propellant
|Muzzle Velocity||2,650 fps (808 mps)|
|Working Pressure||20 tons/in2 (2,150 kg/cm2)|
|Approximate Barrel Life||1,400 rounds|
|Ammunition stowage per gun||Tribals: 200 rounds SAP + 50 rounds
HE and 50 rounds star shell per ship
Others: N/A, but probably similar to Tribals
1) The projectiles were little if any different from those used for the 4.7" (12 cm)/45 Mark I BL, these newer guns being essentially the same weapon converted to use cartridges rather than bag propellants. It is noted by Campbell that "the shells had a mediocre ballistic form." From measuring the sketch shown on the additional picture page, the SAP round appears to be about 3crh.
2) Outfits included SAP, HE and star shells. Ten special anti-submarine HE shells with RDX/TNT fillers were supplied to each ship by 1945 and star shell complement was 150-200 per ship. VT fuzes were supplied starting in 1944 and by the end of the war these equipped about 50% of HE projectiles.
3) Vickers "E" guns fired a slightly lighter projectile of 48.5 lbs. (22 kg) and used a different cartridge case than the RN guns. In Argentine Seville, these guns used a propellant charge of 13.5 lbs. (6.12 kg) CSP2 which gave them a muzzle velocity of 2,789 fps (850 mps). The same projectiles in Brazilian service used a propellant charge of 11.75 lbs. (5.33 kg) MD 19 which gave them a muzzle velocity of 2,658 fps (810 mps).
|Elevation||With 50 lbs. (22.7 kg) HE Shell|
|Range @ 30 degrees||15,800 yards (14,450 m)|
|Range @ 40 degrees||17,000 yards (15,545 m)|
|6,500 yards (5,950 m)||
|Note: Data from "British Battleships of World War Two." Assumes a perpendicular impact.|
(see Notes 6, 7 and 9)
|Single Mountings for Mark IX Guns
Mackay and Bulldog (4): CPXIII
A (4), B (4), C (4), D (4), Codrington (5) and RCN Saguenay (4): CPXIV
(a lighter version of this mounting was later used on sloops)
Submarine wet-mount (1): CPXVI
E(4), F (4), G (4), Exmouth (5), Faulknor (5), Grenville (5) and Hardy (5): CPXVII
H (4), I (4), O (4), Q (4), R (4) and Inglefield (5): CPXVIII
S (4), T (4), U (4), V (4) and W (4): CPXXII
Argentina: Buenos Aires
(4): N/A (possibly CPXVII)
Twin Mounting for Mark XII Guns
Single Mounting for Vickers "E" Guns
CPXIV: 8.64 tons (8.79 mt)
CPXIV (sloops): 8.13 tons (8.26 mt)
CPXVII: 8.83 tons (8.97 mt)
CPXVIII: 9.54 tons (9.70 mt)
CPXXII: 11.58 tons (11.77 mt)
CPXIII: -10 (?) / +60 degrees
CPXIV: -10 / +30 degrees
CPXVI: -10 / +30 degrees
CPXVII: -10 / +40 degrees
CPXVIII: -10 / +40 degrees
CPXXII: -10 / +55 degrees
|Elevation Rate||Single mountings: Manually operated,
Twin mountings: 10 degrees per second
(see Notes 5 and 8)
All but the below: about +150 / -150 degrees
"X" position on S, T, U, V and W classes: 360 degrees
|Train Rate||Single mountings: Manually operated,
Twin mountings: 10 degrees per second
|Gun recoil||All except CPXXII: 26.5 in (67.3
CPXXII: 18 in (45.7 cm)
1) These guns were first tried on HMS Mackay in a clumsy CPXIII mounting which allowed +60 degrees elevation. This particular mounting was removed and then fitted to HMS Bulldog. This mounting was not adopted for British service, but it appears to have been used on ships built for Argentina, Chile and China. This mounting had a 68 inch (173 cm) trunnion height making it difficult to load at low angles. 55 inches (140 cm) is considered the maximum desirable trunnion height for a 50 - 55 lbs. (22.7 - 24.9 kg) projectile.
2) The CPXVII mount achieved +40 degree elevation by having a 14" (35.6 cm) gun well with a removable cover which allowed the breech end to go below the deck level. With the cover in place, the mounting could only elevate to 29.5 degrees. "An obviously makeshift design, one wonders how it managed to make it into a service weapon let alone off the drafting table" - John Campbell in "Naval Weapons of World War Two."
3) The CPXVIII mounting had the balance weight repositioned above the loading tray which allowed +40 degree elevation without the necessity of the gun wells. These mountings used a circular base plate that was directly bolted to the weather deck and were supported underneath by a ring-shaped bulkhead called the "gun support." A lower roller path was machined on the base ring with a similar upper roller path machined into the underside of the mounting turntable platform. A ring of horizontal roller bearings in these paths held the weight of the mounting. At the center of rotation a light cage held vertical thrust roller bearings and the electrical cabling for fire control and lighting ran up through this cage.
4) The CPXIX twin mounting was the first British power mounting specifically designed for destroyers. These guns had a trunnion height 13" (33 cm) higher than the single mountings. This required raising the wheelhouse to enable to helmsman to see over the gun shields. It also made loading the weapons at low elevations more difficult. The gun axes were 38 in (96.5 cm) apart.
5) The Tribal class had their four CPXIX mountings split in two groups, each powered by a 140 HP steam turbine and oil hydraulic pump. The J, K and N classes had a 70 HP electric motor and pump on each individual mounting. Elevation was by a hydraulic motor driving pinions on a common shaft which in turn drove arcs fixed to the gun cradles while training was by a hydraulic motor with a similar worm gear. For unknown reasons, "X" mounting on the "J" class was originally set up such that the mid-training position was dead ahead. This meant that this stern mounting on these ships could not bear directly astern and that having to train from the port quarter to the starboard quarter meant that the gun had to slew "the long way round." Early in the war, the mountings were modified to move the mid-train position to the more normal dead astern position. The other destroyers with these mountings were all completed with the stern mountings mid-train position at dead astern.
6) In order to improve their AA capabilities, four of the "O" class destroyers received old 4" (10.2 cm) guns in lieu of 4.7" (12 cm) guns. The "S" class destroyer HMS Savage did not receive these 4.7" (12 cm) guns as did her sisters, as she was used as a test bed for 4.5" (11.4 cm) guns on destroyers.
7) The mountings used in LCG (L) 3 class, Barracuda and Rochester Castle are unknown.
8) The CPXXII single mounting had a spring-operated rammer, a single-shell fuze setting machine and a shorter recoil stroke. This mounting also enjoyed a higher elevation than in previous mountings, but it was still inadequate for AA purposes. The spring-operated rammer feature was interesting. The rammer spring was cocked by the recoil of the weapon. When the loading tray was pushed across into line with the chamber, the spring tripped automatically and operated the ramming head. This moved the shell and cartridge into the breech while at the same time cocking a smaller "rammer return spring." When the loading tray was moved outwards, ready for reloading, the return spring moved the rammer head to the rear. The automatic tray operation was a large improvement over the earlier hand worked versions, but it needed careful adjustment to ensure that the rammer head tripped at the proper time. These mountings may be easily distinguished from earlier ones by the "raked-back" nature of their front shields, a modification necessitated by their higher maximum elevations. The "X" position for ships with this mounting had modified stops which allowed a total training arc of about 580 degrees. This is why many photographs of these ships show this mounting stowed pointing dead ahead.
9) Most of the Tribal class had "X" mounting removed and a twin 4"/45 (10.2 cm) HA/LA mounting installed in its place in order to increase their anti-aircraft capabilities. For similar reasons, the Abdiel class had their three 4.7" (12 cm) twin mountings replaced with three twin 4"/45 (10.2 cm) HA/LA mountings. Destroyers of the A-I classes reconfigured as ASW escorts had "A" and "Y" guns removed in order to ship more depth charges and to add a Hedgehog launcher. Two RCN Tribal class destroyers were completed after the end of the war with four twin 4"/45 (10.2 cm) HA/LA mountings.
10) Submarine CPXVI mounts were all replaced during the 1930s with standard 4"/40 (10.2 cm) submarine guns. Four CPXVI were converted for use on destroyers and one of these was carried by HMS Acasta.
11) One of the more noticeable features of destroyers with these guns were the large "sprayshields" forward of "B" gun platform and aft of "X" gun platform. Although these structures did reduce spray on the upper decks, their true purpose was to reduce the problem of blast from the upper guns disrupting the crews of the guns on the lower decks. Similar "sprayshields" can be seen on those USN destroyers armed with open 5" (12.7 cm) pedestal mounts. This may be taken as a rather unobvious example of how weapon design influences the design of the rest of the ship. By choosing "lightweight" open mountings for these destroyers, the designers paid a weight penalty in having to add these shield structures. Likewise, the L-M destroyer classes with their "heavyweight" enclosed 4.7" (12 cm) mounts saved some compensating weight by being able to eliminate the blast shields.
12) Gun shields on the Vickers "E" guns were pedestal types with abbreviated shields very similar to those used for the British 4.7"/45 (12 cm) BL Mark I mountings.
15 January 2008 - Benchmark
30 January 2009 - Added construction details
01 January 2010 - Better identified Brazilian and Turkish destroyer classes
20 August 2010 - Added information on Argentine Buenos Aires class
28 February 2012 - Added SAP projectile length and comment regarding crh
14 November 2013 - Added note about use in Netherlands Navy
22 October 2014 - Minor additions