United States of America
3"/50 (7.62 cm) Marks 2, 3, 5, 6 and 8
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Britain
3"/8cwt and 3"/17cwt
Updated 12 Feburary 2012
These were a series of built-up guns dating back to the 1890s.  This was the standard anti-torpedo boat gun of the late pre-dreadnoughts, armored cruisers, destroyers and submarines.  Fired fixed ammunition.

Bethlehem Steel provided twelve guns to Britain during World War I which were known as the 3"/8cwt.   Six additional guns, details unknown, were designated as 3"/17cwt.

During World War II about 350 guns were supplied as part of Lend-Lease.  These were used mainly on DEMS and on three ex-"R" class submarines.

Mark 2 was a built-up weapon with a side-swing carrier breech.  The Mark 3 was of simpler construction but otherwise similar.  Mark 5 had uniform rifling and a Driggs-Seabury semi-automatic vertical sliding breech mechanism.  Mark 6 was similar but with a longer recoil slide.  Mark 8 was a Mark 6 with a horizontally instead of vertically sliding breech block and only one of these guns were built.  Mark 6 Mods 4, 5, 6 and 7 were "wet guns" for submarines.  Mod 6 had a chrome plated slide surface and rear cylinder while the other exposed parts were painted.
WNUS_3-50_mk2_destroyer_pic.jpg

3"/50 (7.62 cm) gun on a US destroyer about 1918
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Click here for additional pictures
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Gun Characteristics
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Designation 3"/50 (7.62 cm) Marks 2, 3, 5, 6 and 8
Ship Class Used On Many ships 1900-1920s
Date Of Design about 1898
Date In Service 1900
Gun Weight Mark 2:  2,086 lbs. (946 kg) with breech
Mark 3:  1,986 lbs. (901 kg) with breech
Mark 5:  2,280 lbs. (1,034 kg) with breech
Gun Length oa N/A
Bore Length 150.3 in (3.816 m)
Rifling Length N/A
Grooves 24
Lands N/A
Twist Marks 2 and 3:  Increasing RH 0 to 1 in 25
Mark 5 and Mark 6:  Uniform RH 1 in 25
Mark 8:  N/A (probably same as Mark 5)
Chamber Volume N/A
Rate Of Fire 15 - 20 rounds per minute
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Ammunition
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Type Fixed
Weight of Complete Round 24 lbs. (10.9 kg)
Projectile Types and Weights Common - 13 lbs. (5.9 kg)
AP Mark 29 Mods 1 and 2 - 13.1 lbs. (5.9 kg)
Bursting Charge Common - 1.27 lbs. (0.58 kg) Black Powder and TNT
AP - 0.3 lbs. (0.14 kg) Explosive D
Projectile Length AP - 12.16 in (30.9 cm)
Common - 12.13 in (30.8 cm)
Propellant Charge
(see Note 2)		 Prior to World War I - 2.7 lbs. (1.2 kg) SPD
During World War II - 3.7 lbs. (1.68 kg) SPD or SPDN
Muzzle Velocity 2,700 fps (823 mps)
Working Pressure 17.0 tons/in2 (2,680 kg/cm2)
Approximate Barrel Life 4,300 rounds
Ammunition stowage per gun Connecticut:  300 rounds
Mississippi:  250 rounds
South Carolina:  300 rounds
Others:  N/A
Notes:

1) During World War II some of the older Mark 2 guns were considered constructionally weak and as a result had their working pressures derated down to 13.0 tons/in2 (2,050 kg/cm2) which reduced their muzzle velocities down to 2,100 fps (640 mps).

2) Some SPD and SPDN cartridges had flashless pellets added which gave them a "reduced" flash.
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Range
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Elevation
With 13 lbs. (5.9 kg) HE
MV = 2,700 fps (823 mps)
Striking Velocity
Angle of Fall
2.0 degrees
3,000 yards (2,740 m)
1,230 fps (375 mps)
3.4
4.3 degrees
4,500 yards (4,150 m)
971 fps (296 mps)
8.4
43 degrees
14,600 yards (13,350 m)
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AA Ceiling
30,400 feet (9,270 m)
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Derated Guns
15 degrees
7,000 yards (6,400 m)
MV = 2,100 fps (640 mps)
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Note:  Time of flight for MV = 2,700 fps (823 mps)
   3,000 yards (2,740 m):  5.1 seconds
   4,500 yards (4,150 m):  9.3 seconds
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Mount / Turret Data
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Designation Pedestal Mounts:  Marks 2, 4, 5 and 7
AA Mount:  Mark 11
Weight  3.0 to 4.2 tons (3.1 to 4.3 mt)
Elevation Marks 2, 4, 5 and 7:  -10 / +15 degrees
Mark 11:  -10 / +85 degrees
Elevation Rate Manually operated, only
Train 360 degrees
Train Rate Manually operated, only
Gun recoil Mark 4:  8 in (20.3 cm)
Mark 5:  9.25 in (23.5 cm)
Mark 7:  16 in (40.6 cm)
Mark 11:  12 in (30.5 cm)
Note:  The Mark 11 was the first 3" (7.62 cm) AA mounting in the USN.  This had a trunnion height of 66.25 inches (168.3 cm) compared to a height of 45 inches (114.3 cm) for the SP pedestal mountings.
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Data from
"Naval Weapons of World War Two" by John Campbell
"US Battleships:  An Illustrated Design History", "US Submarines Through 1945:  An Illustrated Design History", and "US Naval Weapons" all by Norman Friedman
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"Navy Ordnance Activities:  World War 1917-1918" by Navy Dept, United States, Bureau of Ordnance
"Range and Ballistic Tables 1935" by U.S. Department of Ordnance and Gunnery
Page History

31 May 2008 - Benchmark
12 February 2012 - Updated to latest template