46 cm/45 Type 94 naval gun
|46 cm/45 Type 94|
A Type 94 Naval Gun being calibrated on Yamato during construction
|Place of origin||Japan|
|Used by||Imperial Japanese Navy|
|Wars||World War II|
|Designer||C. Hada |
|Manufacturer||Kure Naval Arsenal |
|Barrel length||21.13 m (69 ft 4 in), 46 calibers|
|Diameter||46 cm (18.1 in)|
|Shell||AP Type 91: 1,460 kg (3,218.7 lb)|
HE Type 0: 1,360 kg (2,998.3 lb)
AA Type 3: 1,360 kg (2,998.3 lb)
|Calibre||46 cm (18.1 in)|
|Breech||Welin breech block|
|Recoil||Hydraulic recoil mechanism|
|Elevation||+45/-5 degrees. 10°/s|
|Rate of fire||1.5 - 2 rounds/min|
|Muzzle velocity||780 m/s (2,600 ft/s)|
|Effective firing range||25 km (16 mi)|
|Maximum firing range||42 km (26 mi) at 48° elevation|
The Japanese 46 cm/45 Type 94 naval gun (四十五口径九四式四〇糎砲, Yonjūgo-kōkei kyūyon-shiki yonjussenchi-hō) was a 46 cm (18.1 in) naval rifle, the largest ever mounted on a warship. Only two ships carried them, the Imperial Japanese Navy's World War II super-battleships the Musashi and Yamato. They were designated as a much smaller 40 cm (15.7 in) gun in an effort to hide their true size.
The gun was designed in accordance with the prevailing Japanese naval strategy of Kantai Kessen, the Decisive Battle Doctrine, which presupposed Japan would win a war by fighting and winning a single, decisive naval action. Essential to that victory was being able to out-gun and out-fight its adversary. No other ship could match the firepower and broadside weight of a Yamato-class battleship.
In spite of this, there were no battleship-to-battleship engagements involving either completed vessel of the Yamato-class and an enemy warship. Both were sunk by aerial attack.
The 46 cm (18.1 in) 46 cm/45 Type 94 naval rifle was a wire-wound gun. Nine, mounted in three, three gun turrets, served as the main armament of the Yamato-class battleships that were in service with the Imperial Japanese Navy during World War II. When the turrets and the guns were mounted, each weighed 2,510 tons, which is about the same tonnage as an average sized destroyer of the era.
The Japanese guns were of a slightly larger bore than the three British 18 inch naval guns built during World War I, although the shells were not as heavy. Britain had later designed the N3-class battleship with 18-inch guns but none were built, leaving no Allied naval guns to compare with the Type 94. Unlike most of the very large guns of other navies, they could fire special anti-aircraft shells (Sanshiki) referred to as "beehive".
Some 27 guns were built for the three battleships of the Yamato class. Only 18 were ever shipped, nine each aboard the Yamato and Musashi; the third vessel of the class, the Shinano, was converted into an aircraft carrier and sunk before it entered combat. The complex Type 94 barrels were constructed in three autofrettaged stages. A half-length tube was fitted over the first tube and shrunk onto it. The assembly was then wire wound and two additional tubes shrunk over the entire length of the gun tubes. A final inner tube was then inserted down the gun and expanded into place. This inner tube was then rifled to finish the gun. As designed, this gun could not cost effectively be relined but instead had to have the entire gun tube replaced due to wear.
Unlike previous designs the turrets were found to have nothing in common with previous British Vickers designs used in other Japanese battleships when examined by a US naval technical team. Each gun was independently sleeved allowing for separate elevation. The shell hoists and powder rams were found to be ingenious though unduly heavy designs that allowed a relatively rapid rate of reload. 180 shells (60 rounds per gun) were stored in the turret's rotating structure. The shells were stored vertically and an innovative system of geared mechanical conveyors was employed to move the extremely large and heavy shells from the shell rooms. The mechanical advantage required to move the heavy shells meant these conveyors operated extremely slowly but the 180 shells stored in each turret were considered sufficient for a surface engagement. 
Range and flight time
With Type 91 AP shell
|Elevation||Range||Time of flight|
|10°||18,410 yards (16,830 m)||26.05 sec|
|20°||30,530 yards (27,920 m)||49.21 sec|
|30°||39,180 yards (35,830 m)||70.27 sec|
|40°||44,510 yards (40,700 m)||89.42 sec|
|45°||45,960 yards (42,030 m)||98.6 sec|
Impact angle and velocity
With Type 91 AP shell
|2.4°||5,470 yards (5,000 m)||3.3°||2,264 feet per second (690 m/s)|
|5.4°||10,940 yards (10,000 m)||7.2°||2,034 feet per second (620 m/s)|
|8.6°||16,400 yards (15,000 m)||11.5°||1,844 feet per second (562 m/s)|
|12.6°||21,870 yards (20,000 m)||16.5°||1,709 feet per second (521 m/s)|
|17.2°||27,340 yards (25,000 m)||23°||1,608 feet per second (490 m/s)|
|23.2°||32,810 yards (30,000 m)||31.4°||1,558 feet per second (475 m/s)|
A Type 1 armour-piercing shell at the Yasukuni Shrine in Tokyo.
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- Campbell, John (1985). Naval Weapons of World War Two. Naval Institute Press. ISBN 0-87021-459-4.