Planned for the never-built B-65 class "Super A" cruisers, it appears that no prototypes were ever started. Information on these weapons is based entirely upon the B-65 preliminary design, completed in September 1940. The ships were postponed on 6 November 1941 and officially cancelled following the Battle of Midway in June 1942.

Type 0 (Model 1940) is my estimate, but they may have been designated as Type 94 (Model 1934) if their breech mechanism design followed that of the 46 cm guns used on the Yamato class.

Nomenclature note: "Japanese Cruisers of the Pacific War" states that: "Some sources mention 30 cm, but the actual caliber was to have been 310 mm." This reference further states that 12" (30.5 cm) is "used in non-Japanese publications and non-official Japanese works."

Gun Characteristics

Designation 31 cm/50 (12.2") Type 0 (?) (Model 1940)
Ship Class Used On B-65 class (Warships #795 and 796)
Date Of Design about 1940
Date In Service N/A
Gun Weight N/A
Gun Length oa N/A
Bore Length about 610.2 in (15.500 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume N/A
Rate Of Fire about 3 rounds per minute


Type Bag
Projectile Types and Weights AP - 1,265 lbs. (561 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge N/A
Muzzle Velocity N/A
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun N/A


Range of APC projectiles
Elevation Range
45 degrees 36,000 yards (32,920 m)

Mount/Turret Data

Designation Three-gun Turrets
  B-65 (3)
Weight N/A
Elevation -5 / +45 degrees
Elevation Rate N/A
Train About +150 / -150 degrees
Train Rate N/A
Gun recoil N/A


"Naval Weapons of World War Two" by John Campbell
"Japanese Cruisers of the Pacific War" by Eric Lacroix and Linton Wells II
"Battleships; Axis and Neutral Battleships in World War II" by W.H. Garzke, Jr. and R.O. Dulin, Jr.

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