Photo provided by Mr. Kittel

A series of 3"/50 (7.62 cm) AA guns dating back to the early 1900s.  Successive marks were improved designs.    This was the only dual-purpose gun in the USN's inventory and widely used up to the mid-1930s, but then replaced on larger ships by 5"/38 (12.7 cm) and 40 mm mountings, although the Battleships New York and Arkansas still had them as late as 1943. USS Texas retained the 3"/50 through out WWII.  

Used on many smaller ships such as Destroyer Escorts and Submarines during WWII.

These guns had limited effectiveness in either role, as they were not power operated and so could not be fitted for RPC.  However, the invention of the VT fuse and the Mark 51 director system greatly improved their effectiveness and gave the later marks of this weapon a new lease on life.  In the fall of 1945, CinCPac considered a 3"/50 (7.62 cm) with director control and VT ammunition to be superior to a twin 40 mm mount and at least equivalent to a quad 40 mm mount.
 
Marks 10, 17 and 20 were built up guns with A tube, jacket and hoop.  Mark 18 was made from copper-nickel alloy for wet mountings with A tube, jacket, screwed and shrunk breech housing.  Marks 21 and 22 were very similar apart from a collar on the chase in Mark 22, which was intended a concentric counter-recoil spring fitted only in Mark 24 wartime mountings but used in post-war automatic mountings.  Both had chromium plated bores and had autofretted monoblco barrels secured to the breech housings by bayonet joints.  All used a semi-automatic vertical sliding breech block.

 
 
Gun Characteristics
 
Designation 3"/50 (7.62 cm) Marks 10, 17, 18, 20, 21 and 22
Ship Class Used On Many ships 1910 through 1945
Date Of Design 1908 to 1944
Date In Service 1910 to 1944
Gun Weight 1,760 lbs. (798 kg)
Gun Length oa 159.7 in (4.055 m)
Bore Length 150.3 in (3.816 m)
Number Of Grooves 24
Length Of Rifling 126.1 in (3.204 m)
Chamber Volume 217 in3 (3.56 dm3)
Rate Of Fire 15 - 20 rounds per minute
 
Ammunition
 
Type Fixed
Weight of Complete Round 24 lbs. (10.9 kg)
Projectile Types and Weights HE - 15 lbs. (6.8 kg)
Bursting Charge NA
Projectile Length N/A
Propellant Container Type and Weight Cartridge - 9 lbs. (4.1 kg)
Propellant Charge 3.7 lbs. (1.68 kg)
Muzzle Velocity HE - 2,700 fps (823 mps)
Working Pressure 17.0 tons/in2 (2,680 kg/cm2)
Approximate Barrel Life 4,300 rounds
 
Range
 
Elevation Using 15 lbs. (6.8 kg) HE Shell
Range @ 45 degrees 14,600 yards (13,350 m)
AA Ceiling 30,400 feet (9,266 m)
 
Mount / Turret Data
 
Designation Wet mountings (submarines)
   For Mark 17 guns:  Mark 11
   For Mark 18 guns:  Mark 18
   For Mark 21 guns:  Mark 21

Dry Mountings
   For Mark 10 guns:  Mark 11
   For Mark 20 guns:  Mark 20
   For Mark 21 and 22 guns:  Mark 22 and 24
Weight  3.0 to 4.2 tons (3.1 to 4.3 mt)
Elevation -15 / +85 degrees
Elevation Rate Manually operated, only
Train 360 degrees
Train Rate Manually operated, only
Gun recoil N/A
   
Data from:

www.NavWeaps.com


"US Naval Weapons" by Norman Friedman
"Naval Weapons of WWII" by John Campbell