3"/50 caliber gun

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3 Inch / 50 Cal Gun (Mk 22)
Type	Dual-Purpose Naval Gun
Place of origin	United States
Service history
Used by	US Navy
Specifications
Weight	7,500 lb
Diameter	3"
Crew	7
Shell	AA, AP, Illumination
Elevation	-15 to 85 degrees
Rate of fire	20 rpm
Muzzle velocity	2,700 ft/s
Maximum range	14,600 yards
Sights	Peep-site and Optical telescope

For Army 3-inch gun see 3-inch M1918 gun

The 3"/50 caliber gun (spoken "three-inch-fifty-caliber") in United States naval gun terminology indicates the gun fired a projectile 3 inches (7.62cm) in diameter, and the barrel was 50 calibers long. (barrel length is 3" x 50 = 150" or 3.81 meters)

The 3"/50 caliber gun (Mark 22) was a semiautomatic dual purpose anti-aircraft and surface target weapon used by the U.S. Navy and U.S. Coast Guard from the 1930s through the 1990s on a variety of combatant and transport ship classes with a power driven automatic loader that fired a fixed AA (Anti-aircraft) or HC (High Capacity) round consisting of a projectile and a cartridge case crimped to the projectile. The average weight of the round was 34 pounds. The projectiles weighed about 13 pounds including a burster charge of 0.81 pounds for the AA round and 1.27 pounds for the HC round. The initial velocity of the round was 2,700 feet/second with a maximum range of 14,600 yards at 45 degrees elevation and a ceiling of 29,800 feet at 85 degrees elevation. The gun could fire at a rate of 20 rounds/minute.

The 3" guns were fitted to both single and twin mountings. The single was to be exchanged for a twin 40 mm. mount and the twin for a quadruple 40 mm. mount. Although intended as a one-for-one replacement for the 40 mm. mounts, the final version of the new 3-inch mounts was heavier than expected, and on most ships the mounts could be replaced only on a two-for-three basis. The mounts were of the dual purpose, open-base-ring type. The right and left gun assemblies were identical in the twin mounts. The mounts used a common power drive that could train at a rate of 30 degrees/second and elevate from 15 degrees to 85 degrees at a rate of 24 degrees/second.

The gun was used in single or dual open mounts, designed to replace dual and quad 40 mm antiaircraft guns, respectively. It could fire a 13-pound projectile 14,600 yards in a surface role, and to 29,800 feet as an antiaircraft gun. The rate of fire was about 20 rounds per minute per barrel, which was good against slower planes, but not effective against faster ones such as jets.

The weapon was considered ineffective against surface targets. However, with World War II improvements in fuzing and fire control, a dual 3"/50 mount was considered as effective as a quad Bofors 40 mm gun in the anti-aircraft role. Destroyers that were modernized during the Fleet Rehabilitation and Modernization (FRAM) program of the 1960s had their 3-inch guns removed, but others retained them.

Earlier marks of this gun replaced the original low-angle 4"/50 caliber guns (Mark 9) to provide better anti-aircraft protection for "flush-deck" Wickes and Clemson class destroyers during World War II. The AVD seaplane tender conversions received 2 guns; the APD transport, DM minelayer, and DMS minesweeper conversions received 3 guns, and those retaining destroyer classification received 6.^[1] Their original low-angle 4"/50 caliber guns were transferred to Defensively Equipped Merchant Ships for anti-submarine protection.^[2]

In 1992, The USCGC Storis (WMEC-38) 3"/50 caliber main battery was removed from the cutter. It was the last 3"/50 caliber gun in service aboard any US warship.

[edit] External links

• Destroyer Escort Central: 3"/50 Calibre Gun (Mk 22, Mod 0)
• USS Slater: 3 Inch / 50 Cal Gun (Mk 22) WARNING: Includes loud sounds
• The 3 Inch/.50 Caliber Single Mark 34 and Twin Mark 27/33 Gun Mounts
• HMCS Haida: Two excellent photos
• [1]

[edit] References

• Campbell, John (1985). Naval Weapons of World War Two. Naval Institute Press. ISBN 0-87021-459-4. 
• Silverstone, Paul H. (1968). U.S. Warships of World War II. Doubleday and Company.