Vanguard:  9 rounds per minute

1) As designed, the expected rate of fire for these guns was 10 - 12 rpm.  However, the heavy weight of the projectile and cartridge case plus the semi-automated fuze setting mechanism meant that this round required much crew handling before it could be rammed into the breach.  The tight design of the gunhouse also interfered with the smooth crew operation necessary to achieve high rates of fire.

2) "Battleships:  Allied Battleships in World War II" states that for HMS Vanguard:  "The guns were fully automatic and remotely controlled, with a rate of fire of eighteen rounds per minute."  This ROF figure is sometimes taken to be a per gun value, but no other source supports this claim.  I believe that the "automatic" comment of the authors in this work may have been referring to the automatic fuze setting equipment in the hoists, which was thanks to the Mark 37 GFCS supplied by the USN and similar to that used for the USN 5"/38 (12.7 cm) mountings.  These weapons also had a powered loading tray with automatic ramming link, unlike the manually operated ones used in earlier mountings.  As a result of these improvements, the manual handling by the gun crew would have been significantly lower plus the roomier gunhouse should have allowed freer crew movements.  However, this ROF figure still seems high to me, especially when compared to the post-war 4.5"/45 (11.4 cm) guns on HMS Ark Royal - 15 rpgpm - and to that for the contemporary USN 5"/54 (12.7 cm) Mark 16 - 15 to 18 rpgpm - both of which fired separate ammunition with lighter projectiles and the latter having a superior ammunition feed system and better gun loading arrangements.  For these reasons, I believe that the figure given for Vanguard is probably the combined rate of both guns together and thus the actual ROF per gun would be closer to the figure given in the table above.  This figure still represents a significant 13 to 29% improvement in ROF over the earlier mountings.

3) A proposed light cruiser design in 1944 was to have a modified twin mounting which was to be capable of 12 rounds per minute per gun.  Five of these ships were included in the 1944 program but Adm. Cunningham, the new First Sea Lord, wanted 6 inch (15.2 cm) cruisers, so the five cruisers and their new mountings were cancelled.

1) Outfit included SAP, HE and illumination rounds.  After about 1942, SAP "K" shells were introduced which contained dyes for coloring the shell splashes.  Unlike larger caliber "K" shells, these did not contain a separate fuze and burster for dispersing the dye.

2) Star shell allowance was 400 for battleships and 250 for light cruisers.  Vanguard also had 25 low-angle and 50 high-angle practice rounds per gun.

3) VT fuzed HE was introduced in 1944, equipping up to 50% of the HE rounds by 1945.

RP10 Mark I* and RP10 Mark II:  20 degrees per second

Mark II Mount:  about +150 / -150 degrees 

Vanguard:  about +80 / -80 degrees

RP10 Mark I* and RP10 Mark II:  20 degrees per second

1) The mountings used on the King George V and Dido classes were very cramped and difficult to maintain.  They were also difficult to train in the non-powered mode using the hand mechanisms.  Their rather slow training speeds meant that they could not track fast-moving aircraft.  These last two problems were highlighted during the Japanese attacks on HMS Prince of Wales.  When she took up a 10-11 degree list as a result of damage received, it was found that some of the mounts could not be trained to engage the succeeding attacks.

2) The Mark I mounting used on battleships was a "short trunk" design where the shells and cartridges were sent to a handling room just below the mounting.

3) The following description is adapted from "Naval Weapons of World War Two" by John Campbell:  The ammunition supply for the King George V class was different for end and middle mountings.  In P1, P4, S1 and S4, there were three fixed electric-powered, endless-chain hoists for LA shell, HA shell and cartridges.  These hoists ran from the shell room and magazines to a handling room below each mounting.  Here, shells and cartridges were fed into chutes leading to circular rings around the mounting at working chamber level.  Cartridges were passed to hand-ups to the gunhouse while HA and LA shells were raised by hydraulic pusher hoists for each gun.  The HA hoists raised the shell horizontally to a hand-controlled extension hoist near the inner trunnions.  The shell then rolled into the fuze setting tray and was then passed by hand to the loading tray.  The LA hoists came up in rear of the HA hoists and the shell was raised vertically to be passed by hand to the loading tray.  In P2, P3, S2 and S3, there were two sets of fixed lower hoists with a break and transfer via chutes on the lower deck.  The shell hoists of the lower set were dredger type, with the shells horizontal and not vertical as in the endless-chain hoists.  Otherwise, the supply was the same as for the end mountings.

4) The Mark II mounting used on cruisers was a "long trunk" design with a combined magazine and shell room on one deck.  The trunk contained two HA shell hoists, two LA shell hoists and two cartridge hoists.  All hoists were hydraulic pusher types which delivered shells to the gunhouse as in the Mark I mountings. HA shells were delivered horizontal, while LA shells and cartridges were delivered vertical.

5) RP10 mountings were equipped with RPC.  These mountings had vertical rollers added to steady the turret, the drives in the training and elevating gear were altered to smooth the motions and the loading tray was converted to power operation with an automatic ramming link.

6) The Vanguard's RP10 Mark I* mountings had a larger gunhouse, RPC, fuze setting equipment in the hoists very similar to those for USN 5"/38 (12.7 cm) twin mounts and were tied to the USN Mark 37 GFCS, making for a more successful weapon system.  These mounts also had a joystick for better local control and had the motor and pump moved to the fixed structure in order to lower the revolving weight.  The relative positions of the HA and LA hoists were transposed compared to the other mountings so as to allow the use of Mark VII Metadyne fuze setters, which were located above the HA hoists.  It is noted that these fuze setters were not considered to be very successful.

7) Mounting weights given above include crew and ammunition on the revolving structure.

8) Late in World War II, the two after mountings on the cruiser Argonaut and all eight mountings on the battleship Anson were converted to the RP10 standard.

9) Mark I and Mark II mountings were driven by a 80 bhp (peak 160 bhp) electric motor and oil hydraulic pump mounted on the revolving structure.  Training was by a hydraulic motor with two worm and pinion drives.  Elevation was by a hydraulic motor for each gun which drove a worm gear.  Hand gears were provided for both elevation and training.  Compressed air was used for runout.

10) As noted above, wartime shortages meant that three of the Dido class cruisers were completed with only four instead of five turrets and two others were completed with eight 4.5" (11.4 cm) guns.  For obscure reasons, the third turret on the bow of the Dido class ships was designated as "Q" turret, not "C" turret.  The full set of designations, starting from the bow, went A, B, Q, X and Y.  Somewhat unusually, HMS Bonaventure was completed with turrets in A, B, Q and Y positions, X not being installed.  She was lost in March 1941 before her fifth turret could be installed.  All other eight-gun cruisers, including the follow-on Spartan class, had turrets in A, B, X and Y positions.

11) Following the Bismarck battles, King George V and Prince of Wales had their 5.25" (13.4 cm) mountings modified to improve the watertightness of their mantlet plates.  These changes were incorporated into the rest of the class as they were being built.  Following the loss of Prince of Wales, mountings on the surviving class members had duplicated power leads installed and additional protection worked in to protect the cable entries into the mountings.