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10 cm/65 (3.9") Type 98
Official Designation: 65 caliber Type 98 10 cm Gun
Description
The best Japanese AAA gun of World
War II, whose characteristics can only be described as "superb."
Their only fault was a rather short service life, the result of high muzzle
velocity and a fast rate of fire. In 1945, most new production mounts
were diverted to shore-based installations.
There were two versions of the gun barrel.
Model Type I used a radially expanded, removable lining while the Model
Type I2 was of monobloc construction. Both types had breech
rings and a horizontal sliding breech-block. Spring-operated, semi-automatic
rammers, which were cocked by the recoil force, were mounted above the
guns. These allowed the guns to be loaded at any angle of elevation,
an important factor for any AA weapon. Shells were manually inserted
into fuze setting machines before being placed into the loading trays.
A total of 169 guns were completed between
1940 and 1944 with 68 used in land mountings. All were in twin mounts.
Two mountings were removed from the destroyer Natsuzuki
at the end of the war and sent to the USA for examination.
A new 10 cm (3.9") Type 5 (Model 1945)
gun was under design at the end of the war, but no guns are known to have
been completed. It was intended that this gun would be a replacement
for the 12 cm (4.7") 10th Year Type
used on escort vessels.
Gun Characteristics
| Designation | 10 cm/65 (3.9") Type 98 (Model 1938) Official Designation: 65 caliber Type 98 10 cm Gun |
|---|---|
| Ship Class Used On | Akitsuki, Oyodo, Taiho, Shinano and B-64 classes |
| Date Of Design | 1938 |
| Date In Service | 1942 |
| Gun Weight | 6,731 lbs. (3,053 kg) |
| Gun Length oa | 265.0 in (6.730 m) |
| Bore Length | 255.9 in (6.500 m) |
| Rifling Length | 221.7 in (5.631 m) |
| Grooves | (32) 0.49 in deep x 0.219 in (1.25 mm x 5.565 mm) |
| Lands | 0.167 in (4.252 mm) |
| Twist | Uniform RH 1 in 28 |
| Chamber Volume | 641 in3 (10.5 dm3) |
| Rate Of Fire (see Note) | 15 - 21 rounds per minute |
Akitsuki crewmen reported that 19 rounds per minute
was very difficult to achieve and that 15 was more typical.
Ammunition
| Type | Fixed |
|---|---|
| Weight of Complete Round | HE - 61.7 lbs. (28 kg) |
| Projectile Types and Weights | HE - 28.67 lbs. (13 kg) |
| Bursting Charge | 2.1 lbs. (0.95 kg) |
| Projectile Length | 16.1 in (41 cm) Complete Round: 44 in (111.8 cm) |
| Propellant Charge | 13.2 lbs. (6 kg) 30 DC (?) Cartridge - 33 lbs. (15 kg) |
| Muzzle Velocity | 3,281 fps (1,000 mps) |
| Working Pressure | 19.4 tons/in2 (3,050 kg/cm2) |
| Approximate Barrel Life | 350 - 400 rounds |
| Ammunition stowage per gun | about 400 rounds on larger ships Oyodo: 200 rounds Akitsuki: N/A |
It is interesting to note that, unlike most other naval guns,
the Japanese apparently never developed incendiary shrapnel,
ASW or even illumination rounds for this weapon, implying that it was solely
intended for use as an AA weapon. Practice shells were provided for training
purposes.
Range
| Elevation | Range |
|---|---|
| 45 degrees | 21,325 yards (19,500 m) |
| AA Ceiling @ 90 degrees | 42,651 feet (13,000 m) |
Effective surface range is given as 15,310 yards (14,000 m)
and effective AA range as 12,030 yards (11,000 m).
Mount/Turret Data
| Designation | Twin Mounts Akitsuki (4): Model A Oyodo (4): Model A1 Taiho (6): Model A2 Shinano (8) and B-64 (8): Model A3 |
|---|---|
| Weight | 76,060 lbs. (34,500 kg) |
| Elevation | -10 / +90 degrees |
| Elevation Rate | 16 degrees per second |
| Train | Oyodo, Taiho and B-64: About +/-70 degrees Akitsuki: -150 / +150 degrees |
| Train Rate | 11 - 16 degrees per second |
| Gun recoil | Minimum 16.1 in, nominal 19.3 in, maximum 19.7 in (41 cm, 49 cm and 50 cm) |
| Loading Angle | Any |
- Model A1 was an open mounting
and was used for at least some land mountings. - Mountings used electro-hydraulic power.
Power was supplied by a 15 hp electric motor operating from 220 Vdc and
which ran at 600 rpm. Gun crew for twin mounts was about 11 men. - The Akizuki class used two dredger hoists
to supply ammunition to the working chamber. From here, rounds were
manhandled to loading positions for pusher hoists, one for each gun.
At the top of the hoists, rounds automatically rolled to waiting positions
where shell passers handed them to loaders standing on the gun platform,
which moved with the guns. Fuze-setting machines were attached to
the breech faces of the guns. Loading trays were manually operated. - The Oyodo class used four bucket hoists
which delivered ammunition from the magazines to a working chamber abaft
the No. 2 15.5 cm (6.1") gun barbette.
The maximum rate of supply was 20 to 22 shells per minute per hoist.
The ammunition was then carried by hand to the 10 cm (3.9") gun mounts,
which were 77 and 135 feet (22 and 41 m) further aft. There were
ready-use ammunition storage lockers near the weapon mountings which allowed
for a higher rate of fire for a period of time. The fuze setting
on this class was done by a separate machine before the shells were loaded
into the gun. - Ramming was via a spring-powered mechanism
that was cocked by the recoil force when the gun fired. The mechanism
had a removable pulley arrangement where the gun was depressed to cock
the rammer for the first round. A misfire meant that the subsequent
round needed to be rammed by hand, unless there was time to reattach the
pulley and cycle the gun elevation. The rammer was similar to that
in the earlier 12.7 cm/40 Type 89, but
embodied some improvements, mainly in the tripper gear which had an improved
type of tumbler release mechanism. Early production rammers suffered
frequent failures due to fracturing of the rammer heads, but this problem
was overcome and they gave good service during most of the war. - Distance between gun axes was 26.0 inches
(66 cm).
Additional Pictures
Sources
"Japanese Warships of World War II" by A.J. Watts
"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.
"The Japanese Ships of the Pacific War" by The Koku-Fan
---
US Naval Technical Mission to Japan report O-19: Japanese Projectiles General Types
US Naval Technical Mission to Japan report O-47(N)-1: Japanese Naval Guns and Mounts-Article 1, Mounts Under 18"
---
Japanese Wikipedia 10 cm entry
---
Australian War Memorial Photographs
Page History
26 August 2007 - Benchmark
26 December 2011 - Added information about the 10 cm Type 5
27 May 2012 - Updated to latest template
09 August 2014 - Added comment about mountings from Natsuzuki being sent to USA
27 August 2015 - Added photographs of land emplacement
27 September 2015 - Added mounting designations
25 September 2016 - Converted to HTML 5 format
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