Royal Navy Battle Class 4.5"/45 QF MKIV RP10 Gun x2. Modelled using plans and reference photos from the Vickers Photographic Library. Available in all other scales.
- 2x Mounts
- Accurate Sighting Ports, Rivets, Hex Nuts, Vents, Trunking and Hatches
- Highly detailed and accurate parts, modelled from plans and photographic reference.
- Barrels printed separately and can be angled as desired (Guns were on shared cradle)
These weapons were originally designed to arm the new carriers being built in the 1930s. They were also used on auxiliary vessels and to rearm a few capital ships and then late in the war they became the standard weapon for fleet destroyers.
The Mark I and Mark III guns were used only in twin mountings and were interchangeable with each other, the only difference being in details of the firing mechanism. Several ships actually carried both gun types, depending upon what was available when the ships were being built or modernized. The Mark IV was ballistically identical to the Mark I and Mark III guns but slightly modified in order to fit on the standard 4.7" (12 cm) CP XXII
single mountings used on destroyers and to use separate ammunition. The Mark II was an Army AAA weapon, generally similar to the naval guns but not mounted afloat.
Following the failure of the 5.1"/50 (13 cm) QF Mark I
program, the 4.5" (11.4 cm) caliber was selected in the middle 1930s as the new DP weapon for carriers. It was believed that this was the largest caliber that could be used for a manually-handled fixed round and the complete round for this weapon weighed 85 lbs. (38.6 kg) versus 108 lbs. (49 kg) for the 5.1" (13 cm) gun. However, even though this was a lighter round than that for the 5.1" (13 cm) gun, this decision on the basis of weight was contradictory for two reasons. First, the slightly lighter 4.7" (12 cm) ammunition for destroyers had always been made in separate form in order to reduce the task of the ammunition handlers. Secondly, a fixed round had been designed in the 1920s for the 4.7"/40 (12 cm) Mark XII
anti-aircraft guns used on the Nelson class battleships and this round weighed 74 lbs. (33.6 kg) complete. During service evaluations of the 4.7" (12 cm) Mark XII, it was found that it could not maintain a high rate of fire - a necessity for an AA weapon - as the heavy fixed round rapidly wore out the gun crews. So, if by the early 1930s, it was being found that a 74 lbs. (33.6 kg) fixed round was too heavy to allow sustained rapid firing, then it seems odd that a few years later that an 85 lbs. (38.6 kg) fixed round was deemed to be acceptable. It would appear that the active Navy and the Admiralty had a considerable lack of communications regarding practical experience with fixed ammunition.
Not surprisingly, this fixed round proved to be too heavy in service use and there was a tendency for the projectiles to separate from the cartridge cases during normal handling. These problems resulted in a rapidly decreasing rate of fire during prolonged firing periods.
Learning from war-experience and unlike all previous capital ship twin mountings, the twin mountings designed and built for the post-war carriers Ark Royal and Eagle were modified versions which used separate ammunition.
In 1944, guns of 4.7" (12 cm) caliber, which had been used on nearly every British destroyer built since 1918, gave way to a new destroyer weapon, the 4.5" (11.4 cm) QF Mark IV gun. It had originally been planned that destroyers would also use fixed ammunition, but reports from the cruisers Scylla and Charybdis told of loading problems during rough weather due to the heavy weight of the ammunition. As these were 6,000 ton (6,100 mt) cruisers, it was an obvious conclusion that the much lighter destroyers would have even worse handling problems - a conclusion that the Royal Navy should have been aware of for over a decade. To alleviate the problem, the new 4.5" (11.4 cm) Mark IV destroyer gun was designed to use separate ammunition. Compared to the standard 4.7" (12 cm) Mark IX
, this new destroyer weapon had a higher rate of fire and used a heavier projectile with better ballistic properties, but it is questionable whether these advantages outweighed the disadvantage of adding yet another mid-caliber weapon and its specialized munitions to the already overloaded British logistical system. It did have a post-war advantage in that this new caliber became the standard size for Royal Navy destroyers and continues in use to the present day.
On 8 May 1941 while Renown was engaging Italian torpedo bombers, a fail-safe lockout system malfunctioned and her P3 mounting fired into the back of P2 mounting, killing six and wounding twenty-six crewmembers. Angle iron frameworks were erected by the ship's crew around the mountings to prevent a repeat episode. The fail-safe gear was overhauled during a refit at Rosyth later that same year.
Nomenclature note: In the 1950s the British weapon designation system changed from being per the gun itself to being per the mounting. At the same time, arabic numerals replaced roman numerals. Some confusion was created under this new system because older weapons were redesignated, even though the weapons and mountings themselves did not change. Under this new system, the 4.5-in (11.4 cm) Mark I, Mark III and Mark IV guns
in the Mark II, Mark III, Mark IV and Mark V mountings
were redesignated as Mark 2
and Mark 3
for the twin mounts used on carriers and as Mark 4
(twin) and Mark 5
(single) for the mounts used on destroyers. Asterisks used in the old designation system to denote changes were carried forwards to the new system, but new changes were given "Mod" numbers. This meant that the Royal Navy now had designations such as 4.5-in Mark 5* Mod 2
which meant that this particular mounting had gone through three modifications since it was first designed. As could be expected, these changes have led to much confusion as to what weapons were actually used on any particular ship. For this reason, at the top of this datapage, I show both the original per-the-gun designation and, in parenthesis, the per-the-mounting redesignations.
Gun construction was of an autofretted loose barrel, jacket, removable breech ring and sealing collar. The breech mechanism used a horizontal sliding breech block with hand-operated closing and semi-automatic opening. Mark I had both percussion and electric firing while the Mark III was designed for all-electric firing. The Mark I was later modified to permit electric only firing. The Mark IV used electric firing and the breech mechanism was considerably lighter with more generous radii on some components. Five experimental, 46 Mark I, 524 Mark III and at least 199 Mark IV guns were manufactured. Guns needed to be dismounted in order to change the barrels. It should be noted that these weapons had a relatively short barrel life.
All British 4.5" naval guns have an actual bore diameter of 4.45" (11.3 cm).
Some part cleanup will be necessary. The 3D printing process uses a waxy substance to support certain part features during the printing process. Although the parts are cleaned by Shapeways, some waxy residue may remain. It can be safely removed with water and a mild aqueous detergent like "Simple Green" using an old, soft toothbrush, Q-tips or pipe cleaners. During the printing process, liquid resin is cured by ultraviolet light. Microscopic bits of resin may remain uncured.
Let your parts sit in direct sunlight for a few hours to fully cure the resin.
Water-based acrylic paints meant for plastics is strongly recommended. Other paints, especially enamels, may not cure on Frosted Detail 3D-printed plastics.
Use dedicated model sprue cutters to remove parts to minimise the risk of damage to parts.
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