Japan
6"/50 (15.2 cm) Vickers Mark M
6"/50 (15.2 cm) Mark II and Mark III
15 cm/50 (6") 41st Year Type
Updated 27 May 2012
These guns were originally designed by Vickers as secondary weapons for the battlecruiser Kongo, which was built in Britain by Vickers-Armstrong (Barrow).  The Japanese version was designed by Engineer Hata Chiyokichi and adopted in 1912.  In the Japanese Navy, Vickers built guns were designated as Mark II while those built in Japan were designated as Mark III.

Redesignated in centimeters on 5 October 1917.

When the Kongo class was modernized in the 1930s, these guns were replaced by the new 12.7 cm/40 (5") DP and the 15 cm (6") guns were then reused on the Agano class light cruisers in new twin mountings.  Some coast defense batteries at Guam were also equipped with these weapons.

The Vickers guns were of wire-wound construction but the Japanese ones were of three-layer, built-up construction.  All used screw breech-blocks.

Actual bore size of all guns was 15.24 cm (6.0").  Model No. IV guns were 10.5 cm (4.1") shorter than earlier models.  The data below represents Models I through III guns.
WNJAP_6-50_t41_Kongo_pic.jpg

IJN Kongo in 1929
The 6" (15.2 cm) guns are in casemates along the side
U.S. Naval Historical Center Photograph # NH 85898
WNJAP_14-45_t41_Yamashiro_pic.jpg

Practice shoot on IJN Yamashiro in the 1930s
Photograph copyrighted by Radio Times Hulton Picture Library
WNJAP_6-50_t41_Sakawa_pic.jpg

IJN Sakawa after the war
Note the Type 14 six meter rangefinder in Turret II
In the background are the masts of USS Pecos AO-65
U.S. Marine Corps Photograph 150236, courtesy of U.S. Naval Historical Foundation
WNJAP_6-50_t41_Type_4_pic.jpg

Common Type 4 Projectile
Click on this picture for a larger image
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Images at The Vickers Photographic Archive

See 7195

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Gun Characteristics
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Designation 6"/50 (15.2 cm) Vickers Mark M
6"/50 (15.2 cm) Mark II and Mark III
15 cm/50 (6") 41st Year Type (Model 1908)
Ship Class Used On Kongo, Fuso and Agano classes
Planned for projected light cruisers of the 810 and 5037 classes
Date Of Design about 1910
Date In Service 1913
Gun Weight 18,430 lbs. (8,360 kg)
Gun Length oa 310.1 in (7.876 m)
Bore Length 300.0 in (7.620 m)
Rifling Length 259.2 in (6.584 m)
Grooves (42) 0.050 in deep x 0.300 in (1.27 mm x 7.62 mm)
Lands 0.1488 in (3.78 mm)
Twist Uniform RH 1 in 30
Chamber Volume 1,595 in3 (26.1 dm3)
Rate Of Fire Theoretical:  10 rounds per minute
Effective:  5 - 6 rounds per minute
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Ammunition
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Type Bag
Projectile Types and Weights Common Type 0 HE - 100 lbs. (45.36 kg)
Common Type 4 HE - 100 lbs. (45.36 kg)
ASW - 113.0 lbs. (51.3 kg)
Bursting Charge Common Type 0 HE - 6.4 lbs. (2.9 kg)
Common Type 4 HE - 5.9 lbs. (2.7 kg)
ASW - 6.4 lbs. (2.9 kg)
Projectile Length Common Type 0 HE - 22.9 in (58.0 cm)
Common Type 4 HE - 22.5 in (57.2 cm)
ASW - 23.6 in (60.0 cm)
Propellant Charge Common - 27.3 lbs. (12.4 kg) 37 DC
ASW - N/A
Muzzle Velocity All except ASW - 2,790 - 2,805 fps (850 - 855 mps)
ASW - 820 fps (250 mps)
Working Pressure 18.4 tons/in2 (2,900 kg/cm2)
Approximate Barrel Life 500 - 600 Rounds
Ammunition supply per gun Battleships:  N/A
Agano class:  165 rounds
Notes:

1) Common Type 0 used a nose fuze and was for AA while Common Type 4 used a base fuze and was for ASu.

2) The propellant charge was in one bag with a 2.1 oz (60 gm) black powder igniter.

3) The flat-nosed ASW projectile was issued in 1943 following extensive testing.  This is listed in O-19 as being able to penetrate a 0.3 in (0.8 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 3.1 in (80 cm).
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Range With 100 lbs. (45.4 kg) Common Type 4 Shell
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Elevation
Range
Striking Velocity
Angle of Fall
2.7 degrees
5,470 yards (5,000 m)
1,739 fps (530 mps)
3.8
8.0 degrees
10,940 yards (10,000 m)
1,148 fps (350 mps)
12.5
15.0 degrees
15,420 yards (14,100 m)
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17.5 degrees
16,400 yards (15,000 m)
1,050 fps (320 mps)
28.0
30.0 degrees
 21,330 yards (19,500 m)
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34.0 degrees
21,870 yards (20,000 m)
1,050 fps (320 mps)
52.0
45.0 degrees
22,970 yards (21,000 m)
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Range for other Shells
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Elevation With 100 lbs. (45.4 kg) Common Type 0 Shell
Range @ 45 degrees 22,970 yards (21,000 m)
AA Ceiling at 55 degrees 26,250 feet (8,000 m)
Elevation With 113 lbs. (51.3 kg) ASW Shell
Range @ 40 degrees 4,590 yards (4,200 m)
Note:  Minimum range of ASW shell is given as 875 yards (800 m).  Ranges less than this tended to ricochet.
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Mount / Turret Data
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Designation Single Pedestal Casemate
   Kongo (16):  Vickers P1
   Fuso (16):  N/A

Two gun Mounts
   Agano (3):
Weight  Single Mounts:  N/A

Two-gun turrets:  72 tons (73 mt)
Elevation Kongo and Fuso:  -5 / +30 degrees

Agano:  -5 / +55 degrees 
Elevation Rate Single Mount:  Manual operation, only

Twin Mount:  10 degrees per second
Train Single Mount:  About -70 / +70 degrees

Twin Mount:  about -150 / +150 degrees
Train Rate Single Mount:  Manual operation, only

Twin Mount:  6 degrees per second
Gun recoil N/A
Loading Angle +7 degrees
Notes:

1) The twin gun mounts on the Agano class were not true turrets but enclosed in gun houses with a handling room below.  Shell rooms were located underneath the armored deck with the powder magazines underneath.  The ammunition was moved manually between the magazines and the hoists.  Bags and projectiles were carried by the same bucket hoist and delivered in the vicinity of the handling rooms which were located on the middle deck for mounts 1 and 3 and on the upper deck for mount 2.  Mounts 1 and 2 had two hoists while mount 3 had one hoist.  From the hoists, ammunition was carried by hand through a flashtight door and into the handling room.  From the handling rooms, projectiles were moved to the gunhouse via a pusher hoist while the propellant bags were pushed up by hand to the gunhouse.  Loading was manual with fuzes being set by hand before loading.  A fuze time receiver and fuze setting machine were located near the loading trays.

2) Twin mount gun axes were 61 in (155 cm) apart.
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Data from
"Naval Weapons of World War Two" by John Campbell
"Japanese Cruisers of the Pacific War" by Eric Lacroix and Linton Wells II
"Cruisers of World War Two" and "Battleships of World War Two" both by M.J. Whitley
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"The Japanese Ships of the Pacific War" by The Koku-Fan
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US Naval Technical Mission to Japan report O-19:  Japanese Projectiles General Types
US Naval Technical Mission to Japan report O-54(N):  Japanese Naval Guns
Page History

26 August 2007 - Benchmark
15 June 2010 - Added picture of Common Type 4 projectile
27 May 2012 - Updated to latest template