3″/50 caliber gun

3-inch / 50 caliber gun (Mk 22)
Type Naval gun
Place of origin United States
Service history
Used by US Navy
Specifications
Weight 7,500 pounds (3,400 kg)
Barrel length 12 feet 6 inches (3.81 m) bore (50 calibres)
Crew 7
Shell AA, AP, VT Frag (Variable Timing Fragmentation), Illumination 13 lb (5.9 kg)[1]
Caliber 3-inch (76 mm)
Elevation -15 to 85 degrees
Rate of fire 50 rpm
Muzzle velocity 2,700 ft/s (820 m/s)
Maximum firing range 14,600 yd (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 (76 mm) in diameter, and the barrel was 50 calibers long (barrel length is 3 in × 50 = 150 in or 3.8 m). Different guns (identified by Mark numbers) of this caliber were used by the U.S. Navy and U.S. Coast Guard from 1890[1] through the 1990s on a variety of combatant and transport ship classes.

Early low-angle guns

An early 3"/50 bombarding Veracruz, 1914
USS Pivot firing its forward 3″/50 caliber gun.

The US Navy's first 3″/50 caliber gun (Mark 2) was an early model with a projectile velocity of 2,100 feet (640 m) per second. Low-angle (single-purpose/non anti-aircraft) mountings for this gun had a range of 7000 yards at the maximum elevation of 15 degrees. The gun entered service around 1902 with the Bainbridge-class destroyers, and was also fitted to Connecticut-class battleships. 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 guns (Marks 3, 5, 6, and 19) were originally mounted on ships built from the early 1900s through the early 1920s, and 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.[2]

Dual-purpose guns of the World Wars

3″/50 caliber gun aboard USS Slater

Dual-purpose 3″/50 caliber guns (Marks 10, 17, 18, and 20) first entered service in 1916 as a refit to USS Texas (BB-35) and were subsequently mounted on many types of ships as the need for anti-aircraft protection was recognized. During World War II, they were the primary gun armament on destroyer escorts, patrol frigates, submarine chasers, minesweepers, some fleet submarines, and other auxiliary vessels, and were used as a secondary dual-purpose battery on some other types of ships, including some older battleships. They also replaced the original low-angle 4"/50 caliber guns (Mark 9) on "flush-deck" Wickes and Clemson-class destroyers to provide better anti-aircraft protection. The gun was also used on specialist destroyer conversions; the "AVD" seaplane tender conversions received two guns; the "APD" high-speed transports, "DM" minelayers, and "DMS" minesweeper conversions received three guns, and those retaining destroyer classification received six.[3]

These dual-purpose guns were "quick-firing", meaning that they used fixed ammunition, with powder case and projectile permanently attached, and handled as a single unit weighing 34 pounds (as opposed to older guns and/or heavier guns, in which the shell and powder are handled and loaded separately, which reduces the weight of each handled component, but slows the loading process). The shells alone weighed about 13 pounds including an explosive bursting charge of 0.81 pounds for anti-aircraft (AA) rounds or 1.27 pounds for High Capacity (HC) rounds, the remainder of the weight being the steel casing. 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.[4]

Cold War anti-aircraft gun

3″/50 Mk. 22 in Mk. 22 Mounting in Aalborg Maritime Museum

When multiple hits from Oerlikon 20 mm cannon and Bofors 40 mm guns were unable to prevent kamikaze strikes during the final year of the second world war; the 3"/50 was adapted as a replacement for these weapons. Post-war experimentation with an extended range variant (3"/70 Mark 26 gun) was abandoned as shipboard surface-to-air missiles were developed. The United States Navy considered contemporary 5"/38 caliber guns and 5″/54 caliber guns more effective against surface targets.

Mk. 33 twin mount on USS Wasp, in 1954.

The 3″/50 caliber gun (Mark 22) was a semiautomatic anti-aircraft weapon with a power driven automatic loader. 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. This was performed on Essex-class aircraft carriers, Sumner- and Gearing-class destroyers and other ships circa 1946-50. 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 degree/second and elevate from 15 degrees to 85 degrees at a rate of 24 degree/second. The cannon was fed automatically from an on mount magazine which was replenished during action by two loaders on each side of the cannon.[5]

With proximity fuze and fire-control radar, a dual 3″/50 mount firing 50 rounds per minute per barrel was considered more effective than a quad Bofors 40 mm gun against subsonic aircraft,[6] 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 3″/50 caliber main battery was removed from the cutter. This was supposedly the last 3″/50 caliber gun in service aboard any US warship, but US Navy Charleston-class amphibious cargo ships still retained their forward mounts until the last of the ships, USS El Paso (LKA-117) was decommissioned in 1994. The gun is still in service, however, on some warships of the Philippine Navy, including BRP Rajah Humabon, formerly USS Atherton.

The 17 Asheville-class gunboats mounted a single 3″/50 Mk 34 as their primary armament.

Ships mounting 3″/50 caliber guns

World War II:

Post-World War II:

Notes

  1. 1 2 DiGiulian
  2. 1 2 Campbell 1985 p.146
  3. ↑ Silverstone 1968 pp. 112, 212, 215, 276, 303
  4. ↑ Campbell 1985 p.145
  5. ↑ "The Pouncer Challenges The Sub." Popular Mechanics, April 1955, pp. 88-93, see bottom of p. 90.
  6. ↑ USN Photographic Report 9163, 1948: The New Rapid Fire Navy 8'50 and 3'50 ( You Tube- US Salem Rapid Fire Guns),
  7. ↑ Albrecht 1969 p.320
  8. ↑ Albrecht 1969 p.323
  9. ↑ Blackman 1970 p.521
  10. ↑ Albrecht 1969 pp.322-3
  11. 1 2 Blackman 1970 p.499
  12. 1 2 Blackman 1970 p.519
  13. 1 2 3 Blackman 1970 p.520
  14. ↑ Albrecht 1969 p.327
  15. 1 2 Blackman 1970 p.497
  16. ↑ Albrecht 1969 p.325
  17. 1 2 Blackman 1970 p.493
  18. 1 2 Blackman 1970 p.518
  19. ↑ Blackman 1970 p.457
  20. 1 2 3 4 5 Albrecht 1969 p.324
  21. ↑ Blackman 1970 p.492
  22. ↑ Blackman 1970 p.496
  23. ↑ Blackman 1970 p.456
  24. ↑ Blackman 1970 p.529
  25. ↑ Blackman 1970 p.522
  26. ↑ Blackman 1970 p.495
  27. ↑ Blackman 1970 p.523
  28. ↑ Blackman 1970 p.498
  29. ↑ Blackman 1970 p.490

References

External links

Media related to 3inch/50 Marks 2 3 5 6 8 naval gun at Wikimedia Commons
Media related to 3inch/50 Marks 10-22 naval gun at Wikimedia Commons
Media related to 3inch/50 Marks 27 33 34 AA gun at Wikimedia Commons

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