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
Weight 7,500 pounds (3,400 kg)
Barrel length 150 inches (3.8 m) bore (50 calibres)
Crew 7

Shell AA, AP, Illumination 13 pounds (5.9 kg)[1]
Caliber 3-inch (76 mm)
Elevation -15 to 85 degrees
Rate of fire 20 rpm
Muzzle velocity 2,700 feet per second (820 m/s)
Maximum range 14,600 yards (13,400 m)
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). Different guns (identified by Mark numbers) of this caliber were used by the U.S. Navy and U.S. Coast Guard from 1915[1] through the 1990s on a variety of combatant and transport ship classes.

Earlier guns

USS Pivot (AM-276) firing its forward 3"/50 caliber gun.

The 3"/50 caliber gun (Mark 2) was an early model with a projective velocity of 2,100 feet (640 m) per second. Low-angle mountings for this gun had a range of 7000 yards at the maximum elevation of 15 degrees. By World War II these guns were found only on a few Coast Guard cutters and Defensively Equipped Merchant Ships.[2]

Low-angle 3"/50 caliber gun (Marks 3, 5, 6, and 19) were carried by submarines, auxiliaries, and merchant ships during the second world war. These guns fired the same 2,700 feet (820 m) per second ammunition used by the following dual purpose Marks, but with range limited by the maximum elevation of the mounting. These were built-up guns with a tube, partial-length jacket, hoop and vertical sliding breech block.[3]

3"/50 caliber gun aboard the USS Slater (DE-766)

Dual-purpose 3"/50 caliber gun (Marks 10, 17, 18, and 20) were mounted in fleet submarines and 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.[4] These guns used fixed ammunition (case and projectile handled a single assembled unit) weighing 34 pounds. Projectiles weighed about 13 pounds including a burster charge of 0.81 pounds for Anti-aircraft (AA) rounds or 1.27 pounds for High Capacity (HC) rounds. Maximum range was 14,600 yards at 45 degrees elevation and ceiling was 29,800 feet (9,100 m) at 85 degrees elevation. Useful life expectancy was 4300 effective full charges (EFC) per barrel.[5]

Cold War anti-aircraft gun

The 3"/50 caliber gun (Mark 22) was a semiautomatic anti-aircraft weapon with a power driven automatic loader. The United States Navy considered contemporary 5"/38 caliber guns and 5"/54 caliber guns more effective against surface targets.

These monobloc 3" guns were fitted to both single and twin mountings. The single was to be exchanged for a twin 40 mm antiaircraft gun 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 (76 mm) 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.

With proximity fuze and fire-control radar, a dual 3"/50 mount firing 20 rounds per minute per barrel was considered more effective than a quad Bofors 40 mm gun against subsonic aircraft, but relatively ineffective against supersonic jets and cruise missiles. Destroyers that were modernized during the Fleet Rehabilitation and Modernization (FRAM) program of the 1960s had their 3-inch (76 mm) guns removed, but others retained them. 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. The gun is still in service, however, on select warships of the Philippine Navy.

Ships mounting 3"/50 caliber Mark 22 guns


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External links

  • 1.0 1.1 DiGiulian
  • Campbell 1985 p.146
  • Campbell 1985 p.146
  • Silverstone 1968 pp.112,212,215,276&303
  • Campbell 1985 p.145
  • Albrecht 1969 p.320
  • Albrecht 1969 p.323
  • Blackman 1970 p.521
  • Albrecht 1969 pp.322-3
  • 10.0 10.1 Blackman 1970 p.499
  • 11.0 11.1 Blackman 1970 p.519
  • 12.0 12.1 Blackman 1970 p.520
  • Albrecht 1969 p.327
  • 14.0 14.1 Blackman 1970 p.497
  • Albrecht 1969 p.325
  • 16.0 16.1 Blackman 1970 p.493
  • 17.0 17.1 Blackman 1970 p.518
  • Blackman 1970 p.457
  • 19.0 19.1 19.2 19.3 19.4 Albrecht 1969 p.324
  • Blackman 1970 p.492
  • Blackman 1970 p.496
  • Blackman 1970 p.456
  • Blackman 1970 p.529
  • Blackman 1970 p.522
  • Blackman 1970 p.495
  • Blackman 1970 p.523
  • Blackman 1970 p.498
  • Blackman 1970 p.490