The Type 89 prototype was proved in 1931 and adopted for service use on 6 February 1932.
The Japanese considered the Type 89 to be a good AAA weapon and it had a fast rate of fire and good elevation and training speeds especially on the later Mods. Its primary shortcoming was a relatively low muzzle velocity and thus a short range and low AA ceiling. Used a spring rammer cocked by the recoil, similar to other Japanese AAA weapons.
These weapons were of simple construction with autofretted monobloc barrels and breech rings and used horizontal sliding breech-blocks. Total production of Type 89 guns amounted to 1,306 guns, with 836 being manufactured between 1941 and 1945. Of these, 362 were mounted ashore, including 96 in the Yokosuka area and 54 in the Kure area.
Unless otherwise specified, the data that follows is for the Type 89.
12.7 cm/40 (5") twin mounts on battleship
|Designation||12.7 cm/40 (5") Type 88 (Model 1928)
12.7 cm/40 (5") Type 89 (Model 1929)
|Ship Class Used On||Type 88: Submarines I.5 and I.6
Type 89: Almost all Japanese capital ships, aircraft carriers, heavy cruisers, Matsu and Tachibana class escorts
|Date Of Design||1928 / 1929|
|Date In Service||1932|
|Gun Weight||3.05 tons (3.1 mt)|
|Gun Length oa||208 in (5.284 m)|
|Bore Length||200 in (5.080 m)|
|Rifling Length||175 in (4.450 m)|
|Grooves||(36) 0.060 in deep x 0.261 in (1.52 mm x 6.63 mm)|
|Lands||0.175 in (4.45 mm)|
|Twist||Uniform RH 1 in 28|
|Chamber Volume||549 in3 (9.0 dm3)|
|Rate Of Fire||Type 88: 8 rounds per minute
Type 89: 14 rounds per minute initially, 8 rounds per minute sustained
|Weight of Complete Round||Common Type 0 HE - 75.7 lbs. (34.32 kg)
Common Type 3 IS - 77.2 lbs. (35 kg)
Illum - 75.7 lbs. (34.32 kg)
|Projectile Types and Weights
(see Note 1)
|Common Type 0 HE - 51.7 lbs. (23.45 kg)
Common Type 3 IS - 50.7 lbs. (23.0 kg)
ASW - 46.2 lbs. (20.9 kg)
Illum - 51.7 lbs. (23.45 kg)
|Bursting Charge||Common Type 0 HE - 4.2 lbs. (1.88 kg)
ASW - 8.78 lbs. (4.0 kg)
|Projectile Length||Common Type 0 HE - 17.2 in (43.7 cm)
Common Type 3 IS - 17.2 in (43.7 cm)
ASW - 17.2 in (43.7 cm)
|Complete Round Length||38.2 in (97.1 cm)|
|Cartridge Case Type, Size and Empty Weight||Brass, 127 x 583 mm, about 15.23 lbs. (6.9 kg)|
|Propellant Charge||8.77 lbs. (3.98 kg) 21 DC
Cartridge - 26.3 lbs. (12 kg)
|Muzzle Velocity||Common Type 0 HE - 2,360 - 2,379 fps (700
- 725 mps)
Common Type 3 IS - 2,360 - 2,379 fps (700 - 725 mps)
ASW - 820 fps (250 mps)
Illum - 2,362 fps (720 mps)
|Working Pressure||16 tons/in2 (2,500 kg/cm2)|
|Approximate Barrel Life||800 - 1500 rounds|
|Ammunition stowage per gun||Yamato class: 300 rounds
Cruisers with 4 guns: 250 rounds
Cruisers with 8 guns: 200 rounds
1) IS is my abbreviation for the incendiary shrapnel round (sankaidan) intended for AA use.
2) The flat-nosed ASW projectile was issued in 1943 following extensive testing. This is listed in US Naval Technical Mission to Japan report O-19 as being able to penetrate a 9.85 in (25 cm) plate of Ducol Steel (roughly equivalent to USN HTS) at a depth of 26 feet (8 meters). Range for this performance is not given. However, based upon other errors in this document, I would believe this to be an error in metric to english unit conversion and that the actual performance would more likely be 0.985 in (2.5 cm). ASW may have been issued only to escorts.
3) Illumination rounds were rated at 680,000 candle power and had a maximum range of 15,910 yards (14,550 m) and an effective range of 8,750 yards (8,000 m).
4) Common Type 0 HE had a time fuze and was considered to have an 62.7 foot (18.8 m) effective radius of destruction.
|Elevation||With 50.7 lbs. (23 kg) IS Shell|
|Range @ 45 degrees||16,185 yards (14,800 m)|
|AA Ceiling @ 75 degrees||30,840 feet (9,400 m)|
|Elevation||With 46.2 lbs. (22.0 kg) ASW Shell|
|Range @ 40 degrees||4,700 yards (4,300 m)|
|Note: Minimum range of ASW shell is given as 875 yards (800 m). Ranges less than this tended to ricochet.|
(see Notes 1, 4, 5 and 6)
|Type 88 Single Mounting
I.5 (1): A
I.6 (1): A mod 1
Type 89 Twin Mounts
Type 89 Single Mount
A and A mod 1: 8.7 tons (8.8 mt)
|Elevation||Type 88: - 7 / +75 degrees
Type 89: -7 / +90 degrees (one source says -8 / +85 degrees)
|Elevation Rate||Type 88
Manual operation, only.
|Train||Amidships Mounts: About -70 / +70
Bow and Stern Mounts: About -150 / +150 degrees
|Train Rate||Type 88
Manual operation, only.
|Gun recoil||17.75 in (45.0 cm)|
1) Single mountings were manually operated. All twin mountings were to a generally similar design and used electrically driven oil hydraulic gear for both training and elevation. A loading platform was attached to the rear of the cradle as the trunnions were 98 inches (249 cm) above the roller path. The A1 mount was unshielded. The A1 Mod 1 added a shield, while the shield for the A1 Mod 2 had a slightly different shape and the A1 Mod 3 had a thicker shield. The B1 mounting had no shield but did have a more powerful electric training motor, giving it faster elevation and training speeds.
2) Ramming was via a spring-powered mechanism that was cocked by the recoil force when the gun fired. Fuze-setting machines were fixed to the breech faces of the guns. Most ships had one or two hoists per twin mounting.
3) The submarine mountings were supplied ammunition via pneumatic hoists. Twin mountings on surface ships usually had one or two hoists per mounting, but these were not always located near the guns. For example, the carrier Katsuragi (Unryu class) had one electrical dredger hoist that was located 32 meters (105 feet) and two bulkheads away from the mounting it served.
4) Older battleships of the Kongô, Fuso, Ise and Nagato classes had their 8 cm (3") 41st Year Type and 3rd Year Type AA guns removed during their 1930s rebuilds and replaced with the new 12.7 cm/40 (5") Type 89 in four twin mounts. Kongô and Haruna had two additional twin mountings added in 1944. Ise and Hyuga were given four additional twin mountings in 1943 when they were converted to hybrid carriers. Yamato and Musashi had their two amidships 15.5 cm/60 (6.1") triple mountings removed in 1944 and Yamato was then given six additional 12.7 cm/40 twin mountings in their place, giving her a total of twenty-four 12.7 cm/40 (5") guns. Musashi was also to receive six additional twin mountings, but these were not available prior to her loss.
5) The Japanese plan for those older cruisers equipped with 12 cm/45 (4.7") 10th Year Type secondaries was to rearm them with 12.7 cm/40 (5") Type 89 guns during their 1930s rebuilds. However, this program was only partially completed prior to the start of the Pacific War. It proved impossible to find the weight and space to mount these heavier and larger weapons on the Furutaka and Aoba classes and they retained their four 12 cm/45 guns throughout the rest of their service careers. All four cruisers of the Myôkô class had their six single 4.7 cm/45 guns replaced with four 12.7 cm/40 Type 89 twin mountings during refits in 1934 - 1935. For the Takao class, cruisers Atago and Takao were rearmed with four 12.7 cm/40 twin mountings in 1942. Following damage at Rabul on 5 November 1943 by aircraft from USS Saratoga (CV-3), Maya was sent back to Japan and then converted into an AA cruiser. Her No. 3 turret and all 12 cm/45 AA guns were removed and she was then armed with eight 20 cm (8.0") No. 2 guns and twelve 12.7 cm/40 (5.0") AA guns along with thirty-five 25 mm and thirty-six 13 mm MGs. It had been planned to similarly convert sister-ship Chokai, but this was not carried out and Chokai retained her four 12 cm/45 guns throughout her career. Newer large cruisers starting with the Mogami class were armed with four twin 12.7 cm/40 Type 89 mountings as completed.
6) The three submarine depot ships of the Taigei and Tsurugizaki classes and the two seaplane tenders of the Chiyoda class were originally armed with two twin 12.7 cm/40 (5") mountings as completed. All five of these ships were rearmed with four twin 12.7 cm/40 (5") mountings when they were converted to aircraft carriers during the war.
03 December 2008 - Benchmark
12 March 2011 - Added gun mounting information
18 December 2011 - Added information for minor Japanese warships
16 July 2015 - Added to notes regarding battleship and cruiser rebuilds
27 August 2015 - Added additional pictures datapage