5-inch/25-caliber gun

5"/25 Caliber Gun
On the deck of Balao-class submarine USS Bowfin
Type	Anti-aircraft gun Naval gun
Place of origin	United States
Service history
Used by	US Navy, Argentine Navy
Wars	World War II, Falklands War
Production history
Variants	Mk 10, 11, 13, 17
Specifications
Mass	2 metric tons
Length	11 ft 10 in (3.6 m)
Barrel length	10 ft 5 in (3,175 mm) bore (25 calibers) 8 ft 2 in (2.4 m) rifling
Shell	127 × 626 mm R fixed or semi-fixed 52 to 54.5 lb (23.6 to 24.7 kg)[1]
Caliber	5 in (127 mm)
Elevation	-10° to +85°
Muzzle velocity	2,100 ft/s (640 m/s) average
Effective firing range	14,500 yards (13,300 m) at 40° 27,400 feet (8,400 m) at 85°

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 widespread dual-purpose 5"/38 caliber gun, which was derived from the 5"/25. 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] It is referred to sometimes as a dual-purpose gun and sometimes as an anti-aircraft gun, because of its comparative weakness against surface targets.