Cacertian RN-MBII Naval Gun
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| Royal Navy Main Battery Mark II (RN-MBII) | |
|---|---|
 Guns of the HMS Azalio D'Orio being installed, 1931. | |
| Type | Naval gun |
| Place of origin |  Cacertian Empire |
| Service history | |
| In service | 1932 – 1948 |
| Used by |  Cacertian Royal Navy |
| Wars | Siduri War |
| Production history | |
| Designed | 1930 |
| Manufacturer | CNRC Ordnance Bureau |
| Produced | 1930 - 1937 |
| Specifications | |
| Weight | 120 tons |
| Length | 20 meters |
| Barrel length | 19.3 meters |
| Shell | Separate-loading, case charge |
| Shell weight | AP: 1,200 kg HE: 800 kg |
| Caliber | 405 mm |
| Action | Horizontal sliding block |
| Elevation | -5° to 45° aboard the Amika Carpio-class |
| Traverse | Up to 360° |
| Rate of fire | 2.5 rpm |
| Muzzle velocity | 820 m/s |
| Effective firing range | 36,000 meters with 800 kg HE shell at 30° elevation |
| Maximum firing range | 38,500 meters at 45° elevation |
The Royal Navy Main Battery Mark II was a Cacertian naval gun introduced in the early 1930s and used exclusively on the Amika Carpio-class battleships. They were the originally intended armament of the Andrea Doria-class until the success of the RN-MBIII guns brought about a re-analysis of the new class’ armament. The remaining examples of the RN-MBII can still be found in preserved condition mounted aboard the HMS Amika Carpio at the Fumicino Naval Warfare Musuem.
Description
The 405mm RN-MBII guns were built-up guns designed from the ground up to be a new generation of naval artillery for the Cacertian Royal Navy meant specifically for range and accuracy. The increase in caliber was part of an artillery experiment conducted by Eugenia Davion in her Project 2-4 warship design. The most notable improvement of the gun over it’s predecessors was its ability to fire a 1,200 kg armor-piercing shell at a muzzle velocity of 820 m/s utilizing a full charge.
Each gun barrel was 20,000 mm in length with a bore length of 19,300 mm and a rifling length of 16,800 mm. The guns maximum range was accomplished at an elevation of 45°; 36,000 meters with a heavy armor-piercing shell and 38,500 meters for a lighter high explosive shell. Capable of turning 4° a second, each turret could train 150° port and starboard with a 180° rotation speed of 45 seconds. The guns on turret I, II, and IV were capable of depressing -5°, but due to it’s superfiring position the guns in turret III were locked to depress only to 0°.
Service History
The RN-MBII naval guns saw extensive service during the Great War as the primary armament of the two Amika Carpio-class battleships HMS Amika Carpio and HMS Azalia D’Orio.