Italy
90 mm/50 (3.5") Ansaldo Model 1938
90 mm/50 (3.5") OTO Model 1939
Updated 12 January 2013
Developed by Ansaldo, these two models were similar in design.  The guns had good ballistic properties for their caliber, but the stabilized mountings they were used in were too advanced for their time and were plagued with many technical faults.  The mountings were stabilized in four axes; training, elevation, roll correction and pitch correction.  They required 11 gyros to operate in a very complex arrangement.  RPC was fitted but removed from the Duilo class in 1942, apparently because of water damage.  The Littorio class had their mountings located much higher and retained RPC.

Consisted of autofretted monobloc barrel with a screwed-on breech ring holding the horizontal sliding breech block and seatings for the run-out and recoil cylinders.  The gun barrel was attached to the receiver by a bayonet joint.  The original design was 48 calibers in length, but the production guns were 50 calibers long.

There was also a 90 mm/53 gun produced during the war that was considered to be one of the best Italian AA weapons.  This weapon continued in service until the 1950s.
WNIT_35-50_m1939_pic.jpg

90 mm/50 (3.5") from Caio Duilio now at the Milan Museum of Science and Technique
Picture copyrighted by Eugenio Vajna
WNIT_35-50_m1939_side_pic.jpg

Another view of above 90 mm/50 mounting
Picture copyrighted by Eugenio Vajna
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Gun Characteristics
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Designation 90 mm/50 (3.5") Model 1939
Ship Class Used On Doria and Littorio classes
Prototypes tried on San Giorgio
Manufacturer Ansaldo and OTO
Date of Design 1938
Date In Service 1940
Gun Weight 1.8 tons (1,960 kg)
Gun Length oa N/A
Bore Length 177.2 in (4.500 m)
Rifling Length N/A
Grooves N/A
Lands N/A
Twist N/A
Chamber Volume N/A
Rate Of Fire
(see Note)		 12 rounds per minute
Note:  Well trained guncrews could reach 16 rounds per minute, but 12 rounds per minute was the normal rate.
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Ammunition
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Type Fixed
Weight of Complete Round 40.6 lbs. (18.4 kg)
Projectile Types and Weights AA - 22.5 lbs. (10.1 kg)
Bursting Charge N/A
Projectile Length N/A
Propellant Charge 7.5 lbs. (3.4 kg)
Muzzle Velocity 2,822 fps (860 mps)
Working Pressure 19.37 tons/in2 (3,050 kg/cm2)
Approximate Barrel Life N/A
Ammunition stowage per gun
(see Note 1)		 Littorio:  487 rounds
Others:  N/A
Notes:

1) Outfit for Littorio class was 5,842 AA and 50 illumination rounds.  Handling rooms held 90 ready rounds.

2) Illumination rounds were supplied but these were considered to be inadequate due to their small size.

3) AA rounds were considered to have good ballistic behavior and accuracy, but early rounds fragmented into very small pieces, limiting the effective bursting range.  Rounds with better fragmentation patterns were introduced during the war and these remained in service with the land-based guns into the 1950s.
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Range
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Elevation With 22 lbs. (10 kg) AA shell
Range @ 45 degrees 14,220 yards (13,000 m)
AA Ceiling about 35,400 feet (10,800 m)
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Mount / Turret Data
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Designation Single Mounts
   Doria (10) and Littorio (12)
Weight  18.77 tons (19.07 mt)
Elevation -3 / +75 degrees
Elevation Rate Manual operation, only
Train about +120 / -120 degrees
Train Rate Manual operation, only
Gun recoil 19 in (48.4 cm)
Notes:

1) Two prototype moutnings with 48 caliber guns were tested on the armored cruiser San Giorgio in 1938.

2) Fixed rounds were supplied from the magazine to the main deck by an electric hoist capable of supplying 30 rounds per minute.  Rounds were passed by hand up to a handling room forming the lower compartment of the mounting.  From here, a short hoist attached to the stabilized structure raised the rounds vertically to the gunhouse and then rotated them horizontally.  The hoist was driven by a 2hp electric motor and could be operated at 12, 16 or 30 rounds per minute.  An automatic fuze setter was part of the top of the hoist.  Rounds were loaded by hand with a pantograph link rammer (a mechanical linkage in the style of parallelograms).

3) Roll correction was +/- 14 degrees and pitch correction was +/- 5 degrees.

4) Gunhouses were oval in shape and sharply raked so as to minimize overpressure effects from the main guns.

5) Two unstabilized mountings were planned for arming the fast sloop Diana but these were canceled and she received two old 102 mm/35 (4") guns in their place.
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Data from
"The Littorio Class:  Italy's Last and Largest Battleships 1937 - 1948" by Erminio Bagnasco and Augusto de Toro
"Naval Weapons of World War Two" by John Campbell
"Italian Warships of World War II" by Aldo Fraccaroli
Page History

07 October 2006 - Benchmark
26 May 2012 - Updated to latest template
21 September 2012 - Added mounting information
12 January 2013 - Added notes about rate of fire, ammunition outfit and land based version