United States of America
14"/50 (35.6 cm) Mark 4 and Mark 6
Updated 15 August 2008
A more powerful 14" (35.6 cm) gun used on the New Mexico and Tennessee Class Battleships.  These ships had the first USN triple mounts with individual sleeves for the guns (properly called "three-gun turrets").

During the 1920s the USN had problems with dispersion with these guns at extreme ranges.  The solutions (some possibly apocryphal) involved correcting range tables for errors, introduction of delay coils (to reduce interference in flight) and the reduction of chamber volume to prevent "fall back" of the shell against an incompletely filled chamber.  More importantly, the shot seating was improved to ensure that the shells sat properly when rammed.

During modernizations carried out in the 1930s, most guns were updated and redesignated as 14"/50 (35.6 cm) Mark 11, although USS Tennessee (BB-43) still carried the Mark 4 until 1942.

In the early 1920s, the US Army used the naval 14" (35.6 cm) gun tube to arm the Model 1920 Railroad gun.  This gun could be traversed through seven degrees, giving it the ability to engage moving targets.  The track trucks could be removed and the carriage placed on a circular concrete foundation block which allowed a full 360 degree traverse.  Two of these guns were used in the Panama Canal defenses and were capable of being moved from one ocean to the other in less than a day.

Mark 4 consisted of three hoops, two locking rings, A tube, liner and a screw box liner with a separate screwed on flange.  The Mark 6 was almost identical but had a single step taper liner and uniform twist rifling.  Both had Welin breech blocks that open downwards and used Smith-Asbury mechanisms.
WNUS_14-50_mk4_Mississippi_pic.jpg

USS Mississippi (BB-41) in 1920
WNUS_14-50_mk4_Idaho_pic.jpg

USS Idaho (BB-42) about 1920
U.S. Naval Historical Center Photograph # NH 53203
WNUS_14-50_mk4_Idaho_regun1_pic.jpg

USS Idaho (BB-42) being regunned in late 1920s by Crane Ship No. 1 (ex-USS Kearsarge)
Note the plated over secondary casemates
U.S. Naval Historical Center Photograph # NH 43457
WNUS_14-50_mk4_Idaho_regun2_pic.jpg

USS Idaho (BB-42) being regunned in late 1920s by Crane Ship No. 1 (ex-USS Kearsarge)
Note that the gun house needed to be dismantled in order to change out the guns
U.S. Naval Historical Center Photograph # NH 43458
WNUS_14-50_mk4_RRG_pic.jpg

US Army Model 1920 Railroad Gun in 1924 with Naval 14" (35.6 cm) gun.  Note the carriage outriggers and the projectiles in the foreground.
U.S. Army Ordnance Department Photograph No. 19489
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Gun Characteristics
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Designation 14"/50 (35.6 cm) Mark 4 and Mark 6
Ship Class Used On New Mexico (BB-40) and Tennessee (BB-43) classes
Date Of Design 1916
Date In Service 1918
Gun Weight about 179,614 lbs. (81,473 kg) (including breech)
Gun Length oa 714.0 in (18.136 m)
Bore Length 700 in (17.780 m)
Rifling Length 607.4 in (15.427 m)
Grooves 84
Lands N/A
Twist Mark 4/0:  Increasing RH 1 in 50 to 1 in 32 at the muzzle
Mark 4/3:  Uniform RH 1 in 25
Mark 6:  Uniform RH 1 in 25
Chamber Volume N/A
Rate Of Fire about 1.75 rounds per minute
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Ammunition
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Type Bag
Projectile Types and Weights Early AP - 1,400 lbs. (635.0 kg)
AP Mark 8 Mods 3, 7, 8 and 11 - 1,402 lbs. (635.9 kg)
Common - 1,400 lbs. (635.0 kg)
Bursting Charge Early AP - 31.5 lbs. (14.3 kg) Explosive D
AP Mark 8 - 34.3 lbs. (15.6 kg) Explosive D
Common - about 84.0 lbs. (38.1 kg) Explosive D
Projectile Length AP Mark 8 - 49.44 in (125.6 cm)
Common - about 46.5 in (118.1 cm)
Propellant Charge 470 lbs. (213.2 kg) SPD
Muzzle Velocity 2,800 fps (853 mps)
Working Pressure 18.0 tons/in2 (2,835 kg/cm2)
Approximate Barrel Life 250 rounds
Ammunition stowage per gun 100 rounds
Notes:

1) The AP Mark 8 had a thin cap and a very small windshield.  Common was obsolete by 1915 and no longer in production.

2) Bourrelet diameter was 13.977 inches (35.5 cm).

3) Propellant was in four bags.

4) For data on projectiles used in the late 1930s - 1940s, see the 14"/50 (40.6 cm) Mark 11 data page.
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Range
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Elevation With 1,400 lbs. (635 kg) AP Shell
Range @ 15 degrees about 24,000 yards (21,950 m)
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Armor Penetration with 1,400 lbs. (635 kg) AP Shell
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Range
Side Armor
Deck Armor
6,000 yards (5,490 m)
17.2" (437 mm)
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9,000 yards (8,230 m)
14.4" (366 mm)
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12,000 yards (12,980 m)
11.9" (302 mm)
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16,000 yards (14,630 m)
8.9" (226 mm)
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20,000 yards (18,290 m)
6.7" (170 mm)
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Data is from "Elements of US Naval Guns" of 1918 and General Board file 430 (1916).  It is corrected for angle of fall.
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Mount / Turret Data
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Designation Three-gun Turrets
   New Mexico (4) and Tennessee (4)
Weight N/A
Elevation New Mexico class:  -5 / +15 degrees
Tennessee class:  -5 / +30 degrees
Train 306 max 297 min degrees
Rate of Train N/A
Gun Recoil N/A
Loading Angle New Mexico class:  0 degrees
Tennessee class:  +1 degree
Notes:

1) These three-gun turrets were much improved over the previous triple designs, as their guns were individually sleeved.  The guns could be joined together so that they would elevate as a unit.

2) The distance between gun axes was 71 in (180 cm).

3) Turrets were electrically powered with hydraulic gear.

4) The turrets on the New Mexico class had a 50 hp training motor and a 50 hp elevation motor for each gun.  Ramming was powered by two 90 hp motors, the upper charge hoists were powered by two 7.5 hp motors and the two lower charge hoists by two 10 hp motors.

5) The turrets on the California class had a 50 hp training motor and a 50 hp elevation motor for each gun.  Ramming and the two upper hoists were powered from two 90 hp motors.  The lower hoists were powered from two 7.5 hp motors and the shell hoists from two 35 hp motors.  Originally, there were two shell hoists to supply all three guns, but in the 1930s rebuilds three hoists were installed, each powered by a 35 hp motor, so that each gun had its own shell hoist.  The rotating structure of the turret held a powder room above a shell room.  There were 68 shells stored on their bases in this shell room, with another 33 in the turret proper.  An additional 174 in the space just inside the ring bulkhead and between the stiffeners, on the same level as the shell room.  The powder room above was completely shut off from the shell room and shells traveled through the powder room in an armored tube.  A few shells were stored below the handling room level, 50 on the deck below, 20 within the base of the mounting and 7 in a passageway.  These 77 shells were difficult to get up and into the hoists and should be seen as being more of a reserve stock that would be moved only between engagements.
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Data from
"Naval Weapons of World War Two" by John Campbell
"US Naval Weapons" and "US Battleships:  An Illustrated Design History" both by Norman Friedman
"The Big Gun:  Battleship Main Armament 1860-1945" by Peter Hodges
"Battleships:  United States Battleships, 1935-1992" by W.H. Garzke, Jr. and R.O. Dulin, Jr.
"The Evolution of Battleship Gunnery in the U.S. Navy, 1920-1945" article by William Jurens in Warship International No. 3, 1991
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"Naval Ordnance - A Text Book" revised in 1915 by Lt. Cmdr. Roland I. Curtain and Lt. Cmdr. Thomas L. Johnson
"U.S. Explosive Ordnance:  Ordnance Pamphlet 1664 - May 1947" by Department of the Navy
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Special help from William Jurens, Steve Blake and Bolling Smith