Description

In 1935 the Japanese decided to replace the Vickers 4 cm/62 "HI" (2-pdr) guns because of their slow rate of fire, short effective range, unreliable nature and difficulty of manufacture. A design based upon the French Hotchkiss machine gun was selected as the replacement. French built units, designated as 25 mm Type 94 and Type 95, were tested at the Yokosuka Navy Yard in 1935. The Japanese built version was adopted for service use on 6 August 1936. Japanese modifications included many stainless steel parts for use on submarines, the replacement of some machined parts by castings and the use of Rheinmetall-type flash suppressors.

The 25 mm Type 96 was widely used throughout the Japanese Navy with about 33,000 guns being produced. The Japanese considered this gun to be an excellent weapon, but it did not compare well to either the Bofors 40 mm or the Oerlikon 20 mm weapons used by the Allies. The magazines for the Type 96 held only 15 rounds, so frequent stoppages for change outs were required. By 1945, these weapons fired projectiles too light and too short ranged to effectively engage the heavier and faster US aircraft then in service.

The Japanese were the only major navy of World War II not to develop and deploy any AA machine guns larger than 25 mm (1").

Used a forged monobloc barrel and the automatics were gas-operated.

Gun Characteristics

Designation 25 mm/60 (1") Type 96 (Model 1936)
Ship Class Used On Almost all warships of World War II
Date Of Design 1935 (In Japan)
Date In Service 1936
Gun Weight 253.5 lbs. (115 kg) not including magazine
Gun Length oa 90.4 in. (2.296 m)1
Barrel Length 59.1 in (1.500 m)
Rifling Length 53.2 in. (1.350 m)
Grooves (12) 0.0098 in deep x 0.141 in (0.25 mm x 3.58 mm)
Lands 0.117 in (2.96 mm)
Twist Uniform 1 in 25.2
Chamber Volume N/A
Rate Of Fire 2 Cyclic: 220 - 260 rounds per minute
Effective: 110 - 120 rounds per minute

The barrel was secured to the breech mechanism by screw threads, but the gas cylinder connections made changeouts difficult. Two men using a hammer and a spanner wrench could complete a changeout in about five minutes.

  • ^One source gives a gun length of 96.5 in (2.420 m).
  • ^Cartridge ejection was a problem at high elevations and stoppages were frequent.

Ammunition

Type Fixed
Weight of Complete Round All types about 1.5 lbs. (0.68 kg)
Projectile Types and Weights 1a 2a AP: 0.57 lbs. (0.26 kg)
Common: 0.55 lbs. (0.24 kg)
Incendiary Common: 0.55 lbs. (0.25 kg)
Tracer: 0.55 lbs. (0.25 kg)
Bursting Charge AP and Tracer: None
Common: 0.02 lbs. (0.01 kg)
Incendiary Common: 0.02 lbs. (0.01 kg)
Projectile Length AP: 4.0 in (10.2 cm)
Common: 4.4 in (11.2 cm)
Incendiary Common: 4.3 in (11.0 cm)
Propellant Charge 3.60 - 3.88 oz. (102 - 110 gm) Type 1 No. 2 (K3)
Muzzle Velocity 2,953 fps (900 mps)
Working Pressure 17.1 tons/in2 (2,700 kg/cm2)
Approximate Barrel Life 12,000 rounds
Ammunition stowage per gun 2,000 rounds 3a
  • ^Projectile data from "Japanese Cruisers of the Pacific War." "Naval Weapons of World War Two" says that the AP round weighed 0.62 lbs. (0.28 kg).
  • ^
    Shell Colors
    AP White
    Common Maroon
    Incendiary Common Orange
    Tracer Yellow
  • ^Normal allocation was one tracer in every five rounds.

Range

Range with 0.55 lbs. (0.25 kg) HE
Elevation Distance
45 degrees 7,439 yards (6,800 m)
50 degrees 8,200 yards (7,500 m)
AA Ceiling @ 85 degrees Effective: 9,843 feet (3,000 m)
Maximum: 18,040 feet (5,500 m)

The sources listed below disagree as to the ranges and AA ceiling for this weapon. I have chosen to use those given in "Japanese Cruisers of the Pacific War."

Mount/Turret Data

Designation 1b 2b 3b Single, Twin and Triple Mounts
Weight Single: 1,731 lbs. (785 kg)
Twin: 2,425 lbs. (1,100 kg)
Triple: 3,970 lbs. (1,800 kg)
Elevation -10 / +85 degrees
Elevation Rate Most were manually operated
Some triples had Ward-Leonard RPC: 12 degrees per second
Train 360 degrees
Train Rate Most were manually operated
Some triples had Ward-Leonard RPC: 18 degrees per second
Gun recoil 4.33 in (11 cm)

Triple manually controlled mountings had nine crewmembers (1 pointer, 1 trainer, 1 sight setter and 2 loaders per gun). Twin mountings were similarly manned (seven crewmembers total). Single mountings had three crewmembers (1 gun layer, 1 loader and 1 gun captain).

Apparently, all magazines had to be loaded by hand as no specialized loading equipment was ever developed.

  • ^About 20,000 mountings of all types were produced.
  • ^
    Ship board installations according to O-47(N)-2
    Ship Triples Twins Singles
    Yamato class 40 - 30
    Nagato class 30 - 30
    Ise, Fuso and Kongô classes 20 6 30
    Shokaku class 20 - 30
    Small carriers 40 - 30
    First class (Heavy) cruisers 18 - 16
    Second class (Light) cruisers 12 - 10
    Destroyers 4 4 10
  • ^

    According to US Naval Technical Mission to Japan report O-47(N)-2, the Japanese saw the following deficiencies in these mountings in decreasing order of seriousness:

    1. The multiple mounts could not be trained and elevated rapidly enough, either by power or manual drive.
    2. The gunsights were inadequate against high speed aircraft.
    3. The guns had excessive vibration, making them difficult to keep on target.
    4. The capacity of the ammunition supply equipment was inadequate, causing interrupted fire and a greatly reduced operating routine.
    5. The muzzle blast caused problems for both the guncrew and equipment.

Additional Pictures

Sources

Data from:

  • "Naval Weapons of World War Two" by John Campbell
  • "Battleships: Axis and Neutral Battleships in World War II" by W.H. Garzke, Jr. and R.O. Dulin, Jr.
  • "Japanese Cruisers of the Pacific War" by Eric Lacroix and Linton Wells II
  • "Anatomy of the Ship: The Heavy Cruiser Takao" and "Anatomy of the Ship: The Battleship Yamato" both by Janusz Skulksi
  • "Cruisers of World War Two" by M.J. Whitley
  • "Rapid Fire" by Anthony G. Williams

Other:

  • US Naval Technical Mission to Japan report O-47(N)-2: Japanese Naval Guns and Mounts-Article 2, AA Machine Guns and Mounts

Special help from Nathan Okun

External Resource

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