This weapon was a Vickers design based on the British 2-pdr. Mark VIII (LV) 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. The Japanese "HI" designation for Vickers guns is also translated as "BI" in some accounts.
|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
|Weight of Complete Round
|HE: 2.95 lbs. (1.34 kg)
SAP: 2.95 lbs. (1.34 kg)
|Projectile Types and Weights||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)
Complete round: 11.995 in (30.47 cm)
|Propellant Charge||HE: 0.243 lbs. (0.11 kg)
Cartridge weighed 2.9 lbs. (1.3 kg)
|Cartridge||40 x 158R|
|Muzzle Velocity||HE: 1,969 fps (600 mps)
|Working Pressure||15.5 tons / in2 (2,440 kg / cm2)|
|Approximate Barrel Life||5,000 rounds|
|Ammunition stowage per gun||N/A|
The Japanese did not use the British 2-pdr. HV projectile, their HE projectile was equivalent to the older LV projectile.
|Maximum Surface||6,340 yards (5,800 m)|
|Action Range||3,830 yards (3,500 m)|
|Effective Range||2,190 yards (2,000 m)|
|AA Ceiling @ 85 degrees||13,110 feet (4,000 m)|
Some of the references below credit this gun with a maximum range of 13,000 m (14,220 yards). This seems improbably long for this weapon - for comparison, the much more powerful 40 mm/60 Bofors had a max range closer to 11,400 yards (10,000 m). The "Maximum Surface" and "AA Ceiling" figures above come from US Naval Technical Mission to Japan report O-47(N)-1 and seem more probable but still long. The above "Action Range" and "Effective Range" values come from "Japanese Cruisers of the Pacific War" but again these ranges seem long. The British considered that the "Maximum Effective Range" of the 2-pdr. LV was 1,200 yards (1,100 m) and that the "Maximum Range" was 3,800 yards (3,475 m).
"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"
US Naval Technical Mission to Japan report O-47(N)-1: Japanese Naval Guns and Mounts-Article 1, Mounts Under 18"
"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
Special help from Anthony G. Williams and Paul Roome