Italian
37 mm/54 (1.5") Models 1932, 1938 and 1939
Updated 31 January 2008
This was the standard Italian close-range AA weapon used on larger ships during World War II.  The guns used in the Model 1932 mountings were water-cooled with a recirculating pump, but the others were air-cooled.  The magazines held only six rounds, but it was possible to load them one after the other and thus maintain a high rate of fire.

Differences between models were mainly mounting related.
WNIT_37mm-54_m1932_pic.jpg

37 mm/54 in Model 1932 twin mounting on a Zara Class cruiser
Photograph copyrighted by Elio Andò
WNIT_37mm-54_m1932_museum_pic.jpg

37 mm/54 in Model 1932 twin mounting
Photograph courtesy of Museo Nazionale della Scienza e della Tecnica
WNIT_37mm-54_m1939_pic.jpg

37 mm/54 in what I believe is a RM1939 mounting
Photograph by Aldo Fraccaroli and courtesy of Museo Nazionale della Scienza e della Tecnica
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Image at Museo Tecnico Navale della Spezia

37 mm/54 in single mounting and 37 mm/54 in twin mounting

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Gun Characteristics
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Designation 37 mm/54 (1.5") Models 1932, 1938 and 1939
Ship Class Used On Almost all warships of World War II
Date of Design 1932
Date In Service 1934
Gun Weight 611 lbs. (277 kg)
Gun Length oa N/A
Bore Length 78.7 in (1.998 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Rate Of Fire Selectable:  60, 90 and 120 rounds per minute
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Ammunition
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Type Fixed
Weight of Complete Round N/A
Projectile Types and Weights HE - 3.59 lbs. (1.63 kg)
Bursting Charge N/A
Projectile Length 6.4 in (16.3 cm)
Propellant Charge 0.44 lbs. (0.2 kg)
Muzzle Velocity 2,625 fps (800 mps)
Working Pressure 17.8 tons / in2 (2,800 kg / cm2)
Approximate Barrel Life N/A
Ammunition stowage per gun about 1,500 rounds
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Range
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Elevation With 1.83 lbs. (0.83 kg) HE shell
Range @ 45 degrees 8,530 yards (7,800 m) max.
4,370 yards (4,000 m) effective
AA Ceiling 16,400 feet (5,000 m)
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Mount / Turret Data
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Designation Twin Mounts:  Model 1932 and 1938
Single Mount:  Model 1939 and RM 1939
Weight  Model 1932:  4.9 tons (5.0 mt)
Model 1938:  4.2 tons (4.3 mt)
Model 1939:  1.48 tons (1.5 mt)
RM 1939:  1.97 tons (2.0 mt)
Elevation Singles:  -5 / +90 degrees
Twins:  -10 / +80 degrees
Elevation Rate Manual operation, only
Train about +120 / -120 degrees
Train Rate Manual operation, only
Gun recoil N/A
Notes:

1) Model 1932 was a water-cooled twin mount with a stabilized line of sight through +/-10 degrees of roll.

2) Model 1938 was a twin mount without stabilization or water cooling.

3) Model 1939 was a single collapsible mounting for the forecastles of the Littorio and Duilio classes.

4) RM 1939 was a conventional single mounting.
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Data from
"The Italian Navigatori Class, 1926" article by Elio Andò in "Warship Special 2:  Super Destroyers" edited by Antony Preston
"Naval Weapons of World War Two" by John Campbell
"Battleships:  Axis and Neutral Battleships in World War II" by W.H. Garzke, Jr. and R.O. Dulin, Jr.