Military Wiki
4"/50 caliber naval gun
USS Ward 4 inch gun Minnesota Capitol.jpg
The gun from USS Ward which fired the first American shot of World War II at Pearl Harbor on 7 December 1941
Type Naval gun
Service history
In service 1914 - 1945
Used by  United States
 United Kingdom
Wars World War I, World War II
Production history
Designed 1910
Variants Mk 7, 8, 9 and 10
Weight 5,450 pounds (2,470 kg)
Length 206.5 inches (5.25 m)
Barrel length 200 inches (5 m) bore (50 calibres)

Shell 33 pounds (15 kg)[1]
Calibre 4 inches (100 mm)
Elevation -15 to 20 degrees
Traverse -150 to 150 degrees
Rate of fire 8-9 rpm
Muzzle velocity 2,900 feet per second (880 m/s)[1]
Maximum range 15,920 yards (14,560 m)[1]

The 4"/50 caliber Mark 9 gun (spoken "four-inch-fifty-caliber") was the standard low-angle, quick-firing gun for United States destroyers through World War I and the 1920s. United States naval gun terminology indicates the gun fired a projectile 4 inches (10 cm) in diameter, and the barrel was 50 calibers long (barrel length is 4 inch x 50 = 200 inches or 5 meters).[2]


The built-up gun with a tube, full-length jacket, and side swing Welin breech block with Smith-Asbury mechanism weighed about 2.7 tons. Fixed ammunition (case and projectile handled as a single assembled unit) with a 14.5-pound (6.6 kg) charge of smokeless powder gave a 33-pound (15 kg) projectile a velocity of 2,900 feet per second (880 m/s). Range was 9 miles (14 km) at the maximum elevation of 20 degrees. Useful life expectancy was 500 effective full charges (EFC) per barrel.[1]

Increasing awareness of the need for improved anti-aircraft protection encouraged mounting of dual purpose guns on destroyers beginning in the 1930s. The dual-purpose 5"/38 caliber gun became standard for United States destroyers constructed from the 1930s through World War II. United States destroyers built with 4"/50 caliber low-angle guns were rearmed with dual-purpose 3"/50 caliber guns. The 4"/50 caliber guns removed from destroyers were mounted on British Defensively Equipped Merchant Ships and American armed merchant cruisers ('auxiliary cruisers') like SS Stephen Hopkins.[1]

US Navy service

The 4"/50 caliber gun was mounted on:

UK service

Many Mark 9 guns were supplied to the United Kingdom during World War II as part of Lend-lease, both individually and on naval and merchant ships.[6]

See also


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Campbell 1985 p.143
  2. Fairfield 1921 p.156
  3. 3.0 3.1 3.2 Fahey 1939 p.14
  4. Lenton and Colledge 1968 pp.90-92
  5. 5.0 5.1 Fahey 1939 p.18
  6. Di Giulian


  • Campbell, John (1985). Naval Weapons of World War Two. Naval Institute Press. ISBN 0-87021-459-4. 
  • Fahey, James C. (1939). The Ships and Aircraft of the U.S. Fleet, War Edition. Ships and Aircraft. 
  • Fairfield, A.P. (1921). Naval Ordnance. The Lord Baltimore Press. 
  • Lenton, H.T. and Colledge, J.J. (1968). British and Dominion Warships of World War II. Doubleday and Company. 

External links

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