Italy
3"/50 (7.62 cm) Model 1909
Updated 26 May 2012
A Vickers design used as anti-torpedo boat guns on battleships built before World War I.

Used in a few coastal batteries during World War II.
WNIT_3-50_m1909_Duilio_pic.jpg

3"/50 (7.62 cm) guns on MM Caio Duilio
Photograph copyrighted by Giorgio Giorgerini
WNIT_12-46_m1909_Andrea_Doria_pic.jpg

Forecastle of MM Andrea Doria as viewed from the bridge about 1918
Note the 3"/50 (7.62 cm) anti-torpedo boat guns on both turrets.  In my estimation, this indicates that "B" turret, although in a "superfiring" position, could not actually fire directly over "A" turret, a limitation which was typical of British-designed mountings of the time.
Photograph copyrighted by Giorgio Ciorgerini
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Gun Characteristics
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Designation 3"/50 (7.62 cm) Model 1909
Ship Class Used On Conte di Cavour and Caio Duilio Classes
Date Of Design 1909
Date In Service 1914
Gun Weight 1.1 tons (1.2 mt)
Gun Length N/A
Bore Length 150 in (3.810 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume N/A
Rate Of Fire 10 rounds per minute
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Ammunition
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Type Fixed
Weight of Complete Round N/A
Projectile Types and Weights AP - 13.2 lbs. (6 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge N/A
Muzzle Velocity 2,676 fps (815 mps)
Working Pressure N/A
Approximate Barrel Life N/A
Ammunition stowage per gun About 200 rounds
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Range
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Elevation With 13.2 lbs. (6 kg) AP shell
Range @ 20 degrees 10,930 yards (10,000 m)
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Mount / Turret Data
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Designation Single Mounts
  Cavour (14), Duilio (19)
Weight  N/A
Elevation -10 / +20 degrees
Elevation Rate Manual operation, only
Train 360 degrees
Train Rate Manual operation, only
Gun recoil N/A
Notes:

1) The Cavour class used these guns in open mountings on top of the turrets, forecastle and upper works.  The guns were transferrable and there were 30 positions provided, although they never carried this many guns.  Shortly after World War I they were reduced to 13 guns to provide space for the addition of six 3"/40 (7.62 cm) AA guns.

2) The Duilio class arrangements for these guns were generally similar to the Cavour class with 39 positions provided.  In 1925 they were reduced to 13 of these guns in order to provide for the addition of six 3"/40 (7.62 cm) AA guns.
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Data from
"Naval Weapons of World War Two" by John Campbell
"The Cavour and Duilio Class Battleships" article by Giorgio Giorgerini in "Warship Volume IV"
Page History

01 August 2004 - Benchmark
26 May 2012 - Added ammunition stowage and information about mountings