1/600 Royal Navy 4.5" (11.4cm) RP10 Mark IV x4

1/600 Scale Royal Navy 4.5" (11.4cm) RP10 Mark IV x4 as used by the Royal and Commonwealth Navies on Savage and Battle Class Destroyers. These are highly detailed parts modelled using plans and many reference photographs.

• 4x Mounts
• Highly detailed and accurate parts, modelled from the John Lambert plans and photographic reference
• Details include: Rivets and Hex nuts, Venting, Open Sighting Position, sighting Ports, Crew Access Doors and Ladders
• Barrels are printed separately and can be angled as desired.
  

HISTORICAL DATA
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 Mark II*** BD 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 which was employed in both single and twin mountings. 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, these new destroyer mountings were designed to use separate ammunition. Compared to the standard 4.7" (12 cm) Mark IX, the new destroyer guns 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.

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