Japan
40 mm/62 (1.575") "HI" Type 91
Updated 27 May 2012
This weapon was a Vickers design based on the British 2-pdr. Mark VIII but used on single and twin mountings similar to those used for the British 2-pdr. Mark II mountings.  About 500 guns and 200 mountings were imported from Britain from 1925 to 1935.  Used a 50 round belt although an unsuccessful attempt was made to increase this to 100 rounds.

Like all British 2-pdr. guns, this weapon had a low muzzle velocity and a short effective range.  For that reason, these guns were replaced on most warships starting in 1935 by the Hotchkiss 25 mm gun.

Although this weapon was classified by the Japanese as being 62 calibers long, this dimension was actually the overall length of the weapon.  True bore length of all British 2-pdr guns was 39.37 calibers.
WNJAP_40mm-62_HI_pic.jpg

40 mm "HI" Type 91
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Images of Japanese 2-pdr at The Vickers Photographic Archive

See Vickers 2-pounder and group of 40mm

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Gun Characteristics
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Designation Vickers 40 mm/62 "HI" Shiki
Ship Class Used On Many ships 1925 to 1935
Date Of Design about 1923
Date In Service 1925
Gun Weight 619.5 lbs. (281 kg) including cooling water
Gun Length oa 98.5 in (2.502 m)
Bore Length 62.0 in (1.575 m)
Rifling Length 54.84 in (1.293 m)
Grooves (12) 0.0141 in deep x 0.322 (0.358 x 8.18 mm)
Length Of Rifling 54.84 in (1.293 m)
Twist Uniform RH 1 in 30
Chamber Volume 9.98 in3 (0.165 dm3)
Rate Of Fire 200 rounds per minute cyclical
60 - 100 rounds per minute practical
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Ammunition
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Type Fixed
Weight of Complete Round HE - 2.95 lbs. (1.34 kg)
SAP - 2.95 lbs. (1.34 kg)
Projectile Types and Weights
(see Note)		 HE - 2.0 lbs. (0.9 kg)
SAP - 2.0 lbs. (0.9 kg)
Bursting Charge HE - 0.16 lbs. (0.071 kg)
SAP - 0.05 lbs. (0.023 kg)
Projectile Length N/A
Complete round:  11.995 in (30.47 cm)
Propellant Charge HE - 0.243 lbs. (0.11 kg)
SAP - N/A
Cartridge weighed 2.9 lbs. (1.3 kg)
Cartridge 40 x 158R
Muzzle Velocity HE - 1,969 fps (600 mps)
SAP - N/A
Working Pressure 15.5 tons / in2 (2,440 kg / cm2)
Approximate Barrel Life 5,000 rounds
Ammunition stowage per gun N/A
Notes:

1) The Japanese did not use the British 2-pdr. HE HV projectile, their HE projectile was equivalent to the British LV projectile.

2) Complete breakdown of HE shell weight:

   Empty body:  1.45 lbs. (0.66 kg)
   Driving band:  0.875 oz (0.025 kg)
   Paint:  0.125 oz (0.0035 kg)
   Bursting charge:  2.5 oz (0.071 kg)
   Fuze No 131:  5.25 oz (0.15 kg)
   Total filled:  2 lbs. (0.9 kg)
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Range
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Elevation With 2.0 lbs. (0.9 kg) Shell
50 degrees 14,220 yards (13,000 m)
Action Range 3,830 yards (3,500 m)
Effective Range 2,190 yards (2,000 m)
AA Ceiling @ 85 degrees 22,970 feet (7,000 m)
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Mount / Turret Data
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Designation Single and Twin Mounts
Weight  Single Mount:  1,455 lbs. (660 kg)
Twin Mount:  5,190 lbs. (2,354 kg)
Elevation -5 / +85 degrees
Elevation Rate Manually operated, only
Train 360 degrees
Train Rate Manually operated, only
Gun recoil N/A
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Data from
"Big Gun Monitors:  The History of the Design, Construction and Operation of the Royal Navy's Monitors" by Ian Buxton
"Naval Weapons of World War Two" by John Campbell
"World War II Fact Files:  Anti-Aircraft Guns" by Peter Chamberlain and Terry Gander
"Japanese Cruisers of the Pacific War" by Eric Lacroix and Linton Wells II
"Anatomy of the Ship:  The Heavy Cruiser Takao" by Janusz Skulski"
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"Q.F. High Explosive 2 pdr Mark II N Shell - Forged Steel with Fixing Screw. Design."  No. 21,071.c.(1) / A.D.G.S/3/164 dated 24 February 1916
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Special help from Anthony G. Williams and Paul Roome
Page History

09 April 2007 - Benchmark
27 May 2012 - Updated to latest template