Japan
8 cm/60 (3") Type 98
Updated 27 May 2012
AAA gun used afloat only on the Agano class light cruisers.  Four additional weapons were used as coastal batteries at Maizuru, Kyoto.  Considered to be a satisfactory weapon with no serious problems.  However, it did have a short barrel life.

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 Model Types had breech rings and horizontal sliding breech-blocks.  A total of 28 guns were produced between 1940 and 1944.

Actual bore diameter was 7.62 cm (3.0").
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Gun Characteristics
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Designation 8 cm/60 (3.0") Type 98 (Model 1938)
Ship Class Used On Agano class
Planned for the Ibuki class
Date Of Design 1938
Date In Service 1942
Gun Weight 1.30 tons (1.32 mt)
Gun Length oa 188 in. (4.777 m)
Bore Length 179.78 in (4.567 m)
Rifling Length 159 in. (4.037 m)
Grooves (24) 0.040 in deep x 0.241 in (1.02 mm x 6.12 mm)
Lands 0.152 in (3.85 mm)
Twist Uniform RH 1 in 28
Chamber Volume 213.6 in3 (3.5 dm3)
Rate Of Fire
(see Note 2)		 25 rounds per minute
Notes:

1) The semi-automatic rammer was cocked by the recoil forces when the gun fired.

2) Once the ready rounds were used up, the firing rate was limited by the shell hoists.  These could supply each twin mounting with about 25 rounds per minute, which was about half the theoretical ROF.
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Ammunition
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Type Fixed
Complete Round Weight Type 98 Common HE - 26.5 lbs. (12 kg)
Projectile Types and Weights Type 98 Common HE - 13.2 lbs. (5.99 kg)
Bursting Charge Type 98 Common HE - 0.68 lbs. (0.31 kg)
Projectile Length 12.8 in (32.51 cm)
Complete round:  30.04 in (76.9 cm)
Propellant Charge 4.21 lbs. (1.91 kg)  C2, C3 and DC
Muzzle Velocity 2,953 to 3,018 fps (900 to 920 mps)
Working Pressure 17.8 to 18.4 tons/in2 (2,800 to 2,900 kg/cm2)
Approximate Barrel Life 600 rounds
Ammunition supply per gun 250 rounds
Note:  The sources below differ as to the weight of the propellant charge for these guns.  I have chosen to use the weight given in "Naval Weapons of World War Two."
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Range
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Elevation With 13.2 lbs. (5.99 kg) HE Shell
Range @ 45 degrees 14,870 yards (13,600 m)
AA Ceiling @ 90 degrees 29,850 feet (9,100 m)
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Mount / Turret Data
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Designation Twin Mounts
   Agano (2):  Type A
Weight  12.3 tons (12.5 mt)
Elevation -10 / +90 degrees 
Elevation Rate 16 degrees per second
Train about -150 / +150 degrees
Train Rate 16 - 18 degrees per second
Gun recoil N/A
Loading Angle Any
Notes:

1) Two bucket hoists on the Agano class delivered ammunition to a working chamber on the upper deck abreast the mountings.  Supply was 25 rounds per hoist.  Shells were passed from the working chamber to the guns by hand.

2) The automatic fuze setting apparatus was attached to the breech end of the gun.  This was actuated by hand just before the shell was rammed.
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Data from
"Cruisers of World War Two" by M.J. Whitley
"Naval Weapons of World War Two" by John Campbell
"Japanese Cruisers of the Pacific War" by Eric Lacroix and Linton Wells II
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US Naval Technical Mission to Japan report O-54(N):  Japanese Naval Guns
Page History

04 December 2006 - Benchmark
27 May 2012 - Updated to latest template