United States of America
4"/50 (10.2 cm) Marks 7, 8, 9 and 10
Updated 27 May 2012
These guns were first used as secondary guns on the Arkansas class monitors and then on nearly all of the "Flush-Deck" destroyers as well as on many submarines.  Well-liked on the latter ships, as its light weight made it easy to handle, an important factor on a small ship.

Many individual Mark 9 guns were supplied to the British during World War II as part of Lend-Lease.  In addition, these guns armed numerous ex-USN warships transferred to Britain, including destroyers, submarines, escort carriers and DEMS.  In total 424 guns were transferred to the UK, mainly Mark 9.  The USN also sent 60 guns for Dutch DEMS and 21 guns for Norwegian vessels.  By the end of the war, most Lend-Lease destroyers were reduced to only one 4"/50 (10.2 cm) gun and four escort carriers were rearmed with British 4"/45 (10.2 cm) Mark V guns.  In British service these USN guns had a poor reputation as they were prone to coppering and steel choke problems.  Vickers was asked to provide special liners designed to work with USN ammunition for these guns and for the Mark XVI*, but it was found that this raised the barrel pressure of the latter gun to unacceptable levels.

Mark 7 was constructed of A tube, jacket, hoop locking ring and liner with a screw breech.  Mark 8 was a simplified design consisting of a gun tube and jacket.  Mark 9 was a light weight design for destroyers and submarines and was originally built with A tube and full length jacket with a muzzle swell and used a Smith-Asbury type side swing breech mechanism with a Welin block.  Later mods were of monobloc construction and used chromium plating to increase life.  Mark 10 had a vertically sliding breech block and was intended for anti-aircraft use, but this Mark does not appear to have been put into service.

The data that follows is specifically for the Mark 9 except where otherwise noted.
WNUS_4-50_mk9_Farragut_pic.jpg

Bow gun on USS Farragut DD-300 about 1925
U.S. Naval Historical Center Photograph # NH 98014
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Click here for additional pictures
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Gun Characteristics
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Designation 4"/50 (10.2 cm) Marks 7, 8, 9 and 10
Ship Class Used On Mark 7
Arkansas (BM-7) class

Mark 8
N/A

Mark 9
"Flush Deck" destroyers:  Cassin (D-43), Aylwin (D-47), O'Brien (D-51), Caldwell (D-69), Wickes (D-75) and Clemson (D-186) classes

Submarines:  S-105 ("S" class), Dolphin (SS-169), Shark (SS-174), Perch (SS-176), Salmon (SS-180) and Balao (SS-285 to SS-291) classes

Also used on armed yachts, patrol gunboats, Eagle boats and various auxiliaries

Submarines of the Gato class (SS-212) as refitted
Date Of Design Mark 7 - 1898
Mark 8 - about 1905
Mark 9 - about 1910
Mark 10 - 1914
Date In Service Mark 7 - 1898
Mark 8 - 1906 (?)
Mark 9 -1914
Mark 10 - Not in service
Gun Weight 2.725 tons (2.769 mt)
Gun Length oa 206.5 in (5.2496 m)
Bore Length 200.0 in (5.080 m)
Rifling Length 165.0 in (4.190 m)
Grooves N/A
Lands N/A
Twist Most Marks and Mods:  Increasing RH 0 to 1 in 31.17
Some Mark 9 mods:  Increasing RH 0 to 1 in 25
Mark 9 Mod 11:  Uniform RH 1 in 25
Chamber Volume 654.5 in3 (10.73 dm3)
Rate Of Fire 8 - 9 rounds per minute
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Ammunition
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Type Fixed
Weight of Complete Round 62.4 - 64.75 lbs. (28.3 - 29.4 kg)
Projectile Types and Weights
(see Notes 1 and 2)		 Common Mark 6 Mod 6 - 33.0 lbs. (14.97 kg)
S.P. Common Mark 16 Mods 1 and 2 - 33.0 lbs. (14.97 kg)
H.C. Mark 15 Mod 1 - 33.0 lbs. (14.97 kg)
EX 2 Mods 0 and 1 - 34.0 lbs. (15.4 kg)
Illum Mark 14 Mods 1 through 6 - 34.66 lbs. (15.72 kg)
Bursting Charge Early Common - 1.1 lbs. (0.5 kg) Black Powder
Common Mark 6 Mod 6 - 1.39 lbs. (0.63 kg) Black Powder and TNT
S.P. Common Mark 16 Mods 1 and 2 - 1.16 lbs. (0.53 kg) Explosive D
H.C. Mark 15 Mod 1 - 2.71 lbs. (1.23 kg) Explosive D
EX 2 Mods 0 and 1 - N/A
Projectile Length Common Mark 6 Mod 6 - 15.80 in (40.1 cm)
S.P. Common Mark 16 Mods 1 and 2 - 17.50 in (44.5 cm)
H.C. Mark 15 Mod 1 - 18.00 in (45.7 cm)
EX 2 Mods 0 and 1 - 18.00 in (45.7 cm)
Illum Mark 14 Mods 1 through 6 - 18.40 in (46.7 cm)
Cartridge Case Type, Size and Empty Weight Mark 2 Mod 0 - Brass, 102 x 885 mm, 17.25 lbs. (7.82 kg)
Mark 2 Mod 1 - Brass, 102 x 857 mm, 17.00 lbs. (7.71 kg)
Mark 2 Mod 3 - Brass, 102 x 885 mm, 15.10 lbs. (6.85 kg)
Mark 2 Mod 4 - Brass, 102 x 857 mm, 14.90 lbs. (6.76 kg)
Propellant Charge 14.5 lbs. (6.5 K) SPD 058
15.0 lbs. (6.8 kg) SPD or SPDN
Flashless - 15.0 lbs. (6.8 kg) SPDF
Muzzle Velocity Mark 7 - 2,500 fps (762 mps)
Mark 8 - 2,800 fps (853 mps)
Mark 9 - 2,900 fps (884 mps)
Working Pressure 17 tons/in2 (2,680 kg/cm2)
Approximate Barrel Life Non-chrome plated:  400 to 500 rounds
Chrome plated:  About 600 rounds
Magazine capacity per gun Destroyers:  about 300 rounds
Others:  N/A
Notes:

1) S.P. Common was a "Special Purpose" round having a windscreen and a thin hood and was strengthened to enhance its armor piercing qualities.  The EX-2 Mods 0 and 2 were identical to the HC Mark 15 except that they were 1.0 lbs. (0.45 kg) heavier.  Approximately 18,000 EX projectiles were manufactured and issued.

2) Common Mark 6 and Mark 10 rounds were considered obsolete by 1947.

3) Bourrelet diameter was 3.985 inches (10.12 cm).

4) Britain designed a 6crh HE round of 32 lbs. (14.5 kg) using 14.4 lbs. (6.53 kg) NF/S 198-054 propellant.  This was to give a range of about 14,200 yards (12,980 m) at a muzzle velocity of 2,760 fps (841 mps) at 20 degrees elevation.  It is not thought that this round actually entered service use.
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Range
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Elevation
With 33 lbs. (14.97 kg) AP
MV = 2,900 fps (884 mps)
Striking Velocity
Angle of Fall
0.3 degrees
1,000 yards (910 m)
2,590 fps (789 mps)
0.4
0.7 degrees
2,000 yards (1,830 m)
2,303 fps (702 mps)
0.9
1.3 degrees
3,000 yards (2,740 m)
2,039 fps (621 mps)
1.6
1.8 degrees
4,000 yards (3,660 m)
1,799 fps (548 mps)
2.5
20 degrees
15,920 yards (14,560 m)
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Note:  Time of flight for MV =2,900 fps (884 mps)
   1,000 yards (910 m):  1.1 seconds
   2,000 yards (1,830 m):  2.3 seconds
   3,000 yards (2,740 m):  3.7 seconds
   4,000 yards (3,660 m):  5.3 seconds
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Armor Penetration with 33 lbs. (14.97 kg) AP Shell
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Range
Side Armor
Deck Armor
3,700 yards (3,380 m)
3.0" (76 mm)
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6,300 yards (5,760 m)
2.0" (51 mm)
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18,300 yards (16,730 m)
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1.0" (25 mm)
These figures are taken from armor penetration curves published in 1942.
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Mount / Turret Data
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Designation
(see Note 1)		 Single Mounting
   Arkansas (4):  N/A
   Destroyers (4):  Mark 12
   Submarines (1):  Modified Mark 12

Twin Mounting
   Stockton DD-73 (1), Hovey DD-208 (4) and Long DD-209 (4):  Mark 14
Weight  Mark 12:  4.53 - 5.63 tons (4.60 - 5.71 mt)

Mark 14:  9.41 tons (9.56 mt)
Elevation -15 / +20 degrees
Elevation Rate Manual operation, only
Train about +150 / -150 degrees
Train Rate Manual operation, only
Gun recoil N/A
Notes:

1) The Clemson (DD-186) class had strengthened gun foundations which allowed them to mount heavier weapons.  For this reason, USS Hovey and USS Long were able to use twin 4" (10.2 cm) mounts in place of the single 4" (10.2 cm) mountings used on most other "Flush-deck" destroyers.  USS Stockton was apparently used as a test bed for the twin mounting and had a single twin mount on her bow in 1918.

2) Gato class (SS-212) submarines were originally equipped with 3"/50 (7.62 cm) guns but had these replaced during the war with the 4"/50 (10.2 cm).
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Data from
"Naval Weapons of World War Two" by John Campbell
"US Destroyers:  An Illustrated Design History" and "US Naval Weapons" both by Norman Friedman
"A Treatise on Rifling of Guns" by Carl F. Jeansén
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"Naval Ordnance - A Text Book" revised in 1915 by Lt. Cmdr. Roland I. Curtain and Lt. Cmdr. Thomas L. Johnson
"Range and Ballistic Tables 1935" by U.S. Department of Ordnance and Gunnery
"Ammunition:  Instructions for the Naval Service:  Ordnance Pamphlet 4 - May 1943" by Department of the Navy
"U.S. Explosive Ordnance:  Ordnance Pamphlet 1664 - May 1947" by Department of the Navy
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Gene Slover's Navy Pages
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Special help from Leo Fischer
Page History

15 August 2008 - Benchmark
14 January 2011 - Added data reference
27 May 2012 - Added information regarding use by other nations