5"/25 caliber gun (United States)
The 5"/25 caliber gun (spoken "five-inch-twenty-five-caliber") was the standard anti-aircraft gun for United States Washington Naval Treaty cruisers. 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. 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).
The gun weighed about 2 tonnes 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). Ceiling was 27,400 feet (8352 meters) at the maximum elevation of 85 degrees. Useful life expectancy was 4260 effective full charges (EFC) per barrel. The short barrel of the 5"/25 made it much easier to train against targets. These guns were manually controlled so the short barrel and light weight made it an early favorite as an anti-aircraft gun. The 5"/38 caliber gun replaced the 5"/25 as the anti-aircraft weapon of choice 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 then began being mounted on submarines in late 1943 for extra firepower against small boats and sampans often encountered off the coast of Japan. 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 (13,260 m) at the maximum elevation of 40 degrees.
Ships mounting 5"/25 caliber guns
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- Breyer, Siegfried (1973). Battleships and Battle Cruisers 1905–1970. Doubleday and Company. ISBN 0385-0-7247-0.
- 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.
- 5-INCH GUN MOUNT MARK 40, OP 1029, 1944. Manual for submarine gun & mounting Made available online by Historic Naval Ships Association