Like many British medium-caliber mountings of the 1920s, these guns had a high maximum elevation so that they could engage aircraft, but this was of secondary importance to their use in the anti-ship role. In reality, the training and elevation speeds of the mountings were too slow for the AA role.
The arrangement on the Nelson class had a major disadvantage in that all turrets and their working spaces were grouped tightly together. As the turrets and working spaces were only lightly protected by 1" (25 mm) HT plating, this meant that a single shell could have disabled all guns on one side.
The Mark XXII* was constructed of A tube, taper wound wire, full-length jacket, breech ring and breech bush screwed into the A tube. Used a hand-operated Welin breech block. When this gun was relined with a tapered inner A tube having three locating shoulders, it became the Mark XXII. The later Mark XXII** was built without wire and used an inner A tube. A total of 40 guns were built, including two experimental guns and six Mark XXII**.
P3 Turret on HMS Nelson in 1932
Port 6"/50 (15.2 cm) turrets on HMS Rodney
Interior of a Mark XVIII turret on HMS
|Designation||6"/50 (15.2 cm) BL Mark XXII|
|Ship Class Used On||Nelson Class|
|Date Of Design||about 1921|
|Date In Service||1926|
|Gun Weight||Mark XXII and Mark XXII*
Without Breech: 19,824 lbs. (8,992 kg)
Weight of Breech: 364 lbs. (165.1 kg)
|Gun Length oa||309.7 in (7.866 m)|
|Bore Length||300 in (7.620 m)|
|Rifling Length||255.6 in (6.491 m)|
|Grooves||(36) 0.046 in deep x 0.3759 (1.17 x 9.548 mm)|
|Lands||0.1477 in (3.752 mm)|
|Twist||Uniform RH 1 in 30|
|Chamber Volume||1,750 in3 (28.7 dm3)|
|Rate Of Fire
|5 rounds per minute|
|Note: The original design requirement was for a rate of fire of 7 to 8 rounds per minute. On trials, the best rate achieved was 4 rounds per minute. During her battle with Bismarck, Rodney fired 150 salvos from her starboard battery at an average of 5 salvos per minute and 98 salvos from her port battery at an average of 3.9 salvos per minute. During the first 9 minutes at close range she achieved 5.9 rounds per minute and an output of nearly 100%. In all, Rodney fired 716 rounds of 6" (15.2 cm) CPBC during this action.|
|Projectile Types and Weights||CPBC Mark XXVB - 100 lbs. (45.36 kg)
CPBC (1942) - 112 lbs. (50.8 kg)
HE - N/A
|Propellant Charge||31 lbs. (14.1 kg) SC 150|
|Muzzle Velocity||2,945 fps (898 mps)|
|Working Pressure||20 tons/in2 (3,150 kg/cm2)|
|Approximate Barrel Life||600 rounds|
|Ammunition stowage per gun||Normal: 100 rounds
Maximum: 150 rounds
1) The propellant was in a single bag. Flashless does not seem to have been issued.
2) As of 1942, the same projectiles as used for the Mark XXIII were issued for these guns.
3) Maximum ammunition stowage consisted of 135 CPBC, 15 HE and 24 practice rounds per gun. In addition, there were 72 smoke shells provided per ship.
|Range @ 2.1 degrees||
|Range @ 5.6 degrees||
|Range @ 12.1 degrees||
|Range @ 22.9 degrees||
|Range @ 42.6 degrees||
|Range @ 45.0 degrees||
|Note: Time of flight
for CPBC Shell with MV = 2,900 fps (884 mps)
5,000 yards (4,570 m): 6.2 seconds
10,000 yards (9,140 m): 15.2 seconds
15,000 yards (13,720 m): 28.6 seconds
20,000 yards (18,290 m): 46.1 seconds
25,000 yards (22,860 m): 74.9 seconds
Nelson (6): Mark XVIII
|Weight||168,000 lbs. (76,204 kg)|
|Elevation||-5 / +60 degrees|
|Elevation Rate||8 degrees per second|
|Train||about +100 / -100 degrees|
|Train Rate||about 5 degrees per second|
|Gun recoil||16.5 in (42 cm)|
|Loading Angle||+5 degrees|
1) Telescopic power rammers were used, but the firing cycle was much slower than in earlier mountings.
2) These mountings had very through flash precautions, which may have contributed to the slower ROF. However, the use of turrets meant that much of the ammunition supply could be automated, thus reducing crew fatigue, and they had better arcs of fire both in both the horizontal and vertical planes. As they were mounted on the weather deck, this also meant that they were drier and could function even in heavy seas that would wash out the broadside mounts of earlier designs.
3) Turrets were powered by a 60 bhp electric motor driving a hydraulic pump. A single swashplate engine was used for training while elevation was apparently by a swashplate engine turning a worm gear.
4) The ammunition supply for these mountings was somewhat clumsy. There was a lower magazine with one handling room. Two hoists supplied the working spaces of P1 and S1 turrets (the forward ones on each side), while an upper magazine with two handling rooms and four hoists supplied the working spaces of the other four turrets. The shell room was above the lower magazine and was equipped with six hoists. The charge hoists were endless chains while the shell hoists were of a pusher type, all of which were electrically powered. The upper hoists from the handling rooms to the turrets were hydraulically powered. There was one charge and one shell hoist per gun. Charges were stored in Clarkson's cases and went up the hoist in them and not removed until just before loading. The cases were returned to the working chamber via a tube and then to the magazines by the down side of the lower hoists and through flashtight scuttles.
5) The following comments are from the report by Capt. Thomas Hugh Binney (RN) to the Admiralty upon finishing his tour of command of Nelson in 1930:
In the case of the secondary armament, although the rate of fire is rather low, the increased range at which fire can be opened, and the absence of loss of output due to fatigue, combined with excellent ammunition supply arrangements, will be a very pronounced factor in war.
07 January 2007 - Benchmark
11 February 2012 - Updated to latest template
03 June 2012 - Added mounting notes, added comments by Capt. Binney
05 January 2014 - Added photographs of turrets on HMS Rodney