5"/25 caliber gun

The 5"/25 caliber gun (spoken "five-inch-twenty-five-caliber") entered service as the standard heavy anti-aircraft (AA) gun for United States Washington Naval Treaty cruisers commissioned in the 1920s and 1930s. The goal of the 5"/25 design was to produce a heavy AA gun that was light enough to be rapidly trained manually.[2] The gun was also mounted on pre-World War II battleships and aircraft carriers until replaced by the standard dual-purpose 5"/38 caliber gun, which was derived from the 5"/25 and was similar except for the barrel length. Guns removed from battleships were probably converted for submarine use by late 1943, while a purpose-built variant for submarines was available in mid-1944, and was widely used by them.[3] United States naval gun terminology indicates the gun fired a projectile 5 inches (127 mm) in diameter, and the barrel was 25 calibers long (that is, for a 5" bore and a barrel length of 25 calibers, 5" x 25 = 125", or about 3.2 meters).[4]

5"/25 Caliber Gun
TypeAnti-aircraft gun
Naval gun
Place of originUnited States
Service history
Used byUS Navy, Argentine Navy
WarsWorld War II, Falklands War
Production history
VariantsMk 10, 11, 13, 17
Specifications
Mass2 metric tons
Length11 ft 10 in (3.6 m)
Barrel length10 ft 5 in (3,175 mm) bore (25 calibers)
8 ft 2 in (2.4 m) rifling
Shell52 to 54.5 lb (23.6 to 24.7 kg)[1]
Caliber5 in (127 mm)
Elevation-10° to +85°
Muzzle velocity2,100 ft/s (640 m/s) average
Effective firing range14,500 yards (13,300 m) at 40°
27,400 feet (8,400 m) at 85°

History
Battleship USS New Mexico's 5"/25 battery prepares to fire during the bombardment of Saipan, 15 June 1944

The gun weighed about 2 metric tons and used fixed ammunition (case and projectile handled as a single assembled unit) with a 9.6-pound (4.4 kg) charge of smokeless powder to give a 54-pound (24 kg) projectile a velocity of 2100 feet per second (640 m/s). The ceiling was 27,400 feet (8,400 m) at the maximum elevation of 85 degrees. Useful life expectancy was 4260 effective full charges (EFC) per barrel.[3] The short barrel of the 5"/25 made it much easier to train manually against fast-moving targets. These guns were manually controlled so the short barrel and light weight made it an early favorite as an anti-aircraft gun. Another key feature was power loading, allowing rapid fire at high elevation angles. The 5"/38 caliber gun replaced the 5"/25 as the anti-aircraft weapon of choice on new construction by the mid-1930s due to its better range, velocity against surface targets, and higher vertical ceiling.

5"/25 guns removed from pre-war battleships (especially those rebuilt after Pearl Harbor) had their barrel linings chromed. These guns were remounted for submarine use beginning in late 1943 for extra firepower against small boats and sampans often encountered off the coast of Japan and elsewhere in the Pacific Theater, replacing the earlier 3-inch and 4-inch guns. New production Mark 17 5"/25 guns on the Mark 40 mount designed for submarines became available in mid-1944; USS Spadefish was the first submarine built with this gun. Some submarines had two of these weapons.[2] The Mark 17 gun in the Mark 40 submarine gun mount used semi-fixed ammunition (case and projectile handled separately) and had a range of 14,500 yards (13,300 m) at the maximum elevation of 40 degrees.[5] The submarine mounting had manual elevation, train, and loading with no power assist.

From late 1944 some submarines were built or refitted with two of these weapons. The first of these was USS Sennet, commissioned on 22 August 1944. In February–March 1945 she operated with two other two-gun submarines, USS Haddock and USS Lagarto, in a wolfpack with significant success.[6] To further improve the effectiveness of the two-gun configuration, seven submarines were fitted with a Mark 6 "Baby Ford" fire control computer with a Mark 6 stable element to correct for pitch and roll.[7][8] The first of these was USS Sea Cat, followed by Flying Fish, Entemedor, Sea Dog, Sea Poacher, Sea Robin, and Sennet. However, some of these refits were completed in September 1945, too late to see action.[6]

Ships mounting 5"/25 caliber guns
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See also

Notes
  1. United States of America 5"/25 (12.7 cm) Marks 10, 11, 13 and 17
  2. DiGiulian, Tony (September 2012). "United States of America 5"/25 (12.7 cm) Mark 10". navweaps.com. Retrieved 10 August 2013.
  3. Campbell 1985 p.137
  4. Fairfield 1921 p.156
  5. Campbell 1985 p.138
  6. Friedman 1995, pp. 218-219
  7. Mark 6 computer at Glenn's Computer Museum
  8. Mark 6 stable element manual
  9. Fahey 1941 p.9
  10. Friedman 1983 p.390
  11. Friedman 1983 p.391
  12. Breyer 1973 p.210
  13. Breyer 1973 p.214
  14. Breyer 1973 p.219
  15. Breyer 1973 p.226
  16. Breyer 1973 p.230

References
  • Breyer, Siegfried (1973). Battleships and Battle Cruisers 1905–1970. Doubleday and Company. ISBN 978-0-385-07247-2.
  • Campbell, John (1985). Naval Weapons of World War Two. Naval Institute Press. ISBN 0-87021-459-4.
  • Fahey, James C. (1941). The Ships and Aircraft of the U.S. Fleet, Two-Ocean Fleet Edition. Ships and Aircraft.
  • Fairfield, A.P. (1921). Naval Ordnance. The Lord Baltimore Press.
  • Friedman, Norman (1983). U.S. Aircraft Carriers. Naval Institute Press. ISBN 0-87021-739-9.
  • Friedman, Norman (1995). U.S. Submarines Through 1945: An Illustrated Design History. Annapolis, Maryland: United States Naval Institute. ISBN 1-55750-263-3.
  • Silverstone, Paul H. (1965). U.S. Warships of World War II. Ian Allan Ltd.
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