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 1900 through to 1990 on a variety of combatant and transport ship classes.[3]
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 1900 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.[4]
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-foot-per-second (820 m/s) 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.[4]
Dual-purpose 3"/50 caliber guns (Marks 10, 17, 18, and 20) first entered service in 1915 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.[5]
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.[6]
This is not to be confused with the "rapid-fire" of later gun mounts that used an autoloader mechanism to insert the fixed QF ammunition into the breech. This in turn is not to be confused to a fully automatic gun. The autoloader was still manually filled with shells.
Submarine deck guns
The 3"/50 caliber gun Marks 17 and 18 was first used as a submarine deck gun on R-class submarines launched in 1918–1919. At the time it was an improvement on the earlier 3"/23 caliber gun.[7] After using larger guns on many other submarines, the 3"/50 caliber gun Mark 21 was specified as the standard deck gun on the Porpoise- through Gato-class submarines launched in 1935–1942. The small gun was chosen to remove the temptation to engage enemy escort vessels on the surface.[8] The gun was initially mounted aft of the conning tower to reduce submerged drag, but early in World War II it was shifted to a forward position at the commanding officer's option. Wartime experience showed that larger guns were needed. This need was initially met by transferring 4"/50 caliber guns from S-class submarines as they were shifted from combat to training roles beginning in late 1942. Later, the 5"/25 caliber gun, initially removed from battleships sunk or damaged in the attack on Pearl Harbor and later manufactured in a submarine version, became standard.[9]
During the final year of the Second World War, it was found that multiple hits from Oerlikon 20 mm cannon and Bofors 40 mm guns were often unable to shoot down high-speed Japanese kamikaze aircraft at short ranges before they hit Allied ships; the 3-inch/50 caliber gun was adopted as a more powerful replacement for these weapons.
The 3-inch/50 caliber gun (Mark 22) was a semiautomatic anti-aircraft weapon with a power-driven automatic loader and was fitted as single and twin mounts. The single mount was to be exchanged for a twin 40 mm antiaircraft gun mount, and the twin 3-inch/50 for a quadruple 40 mm mount, on Essex-class aircraft carriers, and Allen M. Sumner and Gearing-class destroyers. Although intended as a one-for-one replacement for the 40 mm mounts, the new 3-inch (76 mm) mounts were heavier than expected, and on most ships, the mounts could only replace Bofors guns on a two-for-three basis. The mounts were of the dual purpose, open-base-ring type and the right and left gun assemblies were identical. 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. The cannon was fed automatically from an on-mount magazine which was replenished by two loaders on each side of the cannon.[10]
Mk. 33 Mod. 13 enclosed twin mount on USS Blue Ridge, in 1991.
The 3-inch/50 was standard-issue on at least 63 classes of ships that have a strong association with World War II.
The total number of vessels amounts to
10 light cruisers
119 submarines (est. maximum 119 installed)
498 destroyer escorts and frigates (1494 installed, 111 removed)
1110 patrol boats, mine sweepers and submarine chasers (1110 up to 1453 installed)
Submarines listed here were built in the 1930s under the limitations of the Washington Naval Treaty and its successors during a period of isolationism and economic austerity. The division into classes was typically a result of construction during a particular fiscal year, but the number built each year was small.
The Gatos became a mass-produced iteration of this line of research and development, because they coincided with the Two-Ocean Navy Act.
Starting with the Balao class of submarines, the 5-inch/25-caliber gun became the standard deck gun of the US Navy
Destroyer escorts were a relative late-comer with production commencing in 1942
Thus they were all mass-produced. They were quick to build and entered service in 1943.
Later war-time classes had a main armament of two 5-inch/38, APD conversions had one such gun. Separation into classes is a result of different propulsion systems used and whether or not torpedoes were carried.
3 guns per vessel
probably all manually loaded Mark 21 or Mark 22
65 Evarts (diesel-electric, short hull, no torpedoes)
Converted destroyers of the WW1-era Wickes and Clemson classes were equipped with 3-inch/50 guns while being converted to high speed transports (3 guns), minelayers (3), minesweepers (3) or seaplane tenders (2).
Patrol boats of less than 1000 tons, some of which were wooden boats. These minesweepers were equipped with anti-submarine warfare equipment and their designs are closely related to the submarine chasers. Submarine chasers can be characterized as smaller, cheaper, coastal waters destroyer escorts. All ships in this group used diesel propulsion.
Restigouche-class destroyers – built with one Mark 33 twin mount aft, those refitted to the Improved Restigouche configuration had them removed (Canada)
Rigel-class stores ships – built with 2 twin mounts[24]
^The Farragut class is sometimes referred to as Coontz-class, because the fourth ship of the class—USS Coontz, designed ordered as a guided missile destroyer variant—was completed first.
Friedman, Norman (1983). U.S. Aircraft Carriers: An Illustrated Design History. Annapolis, Maryland: Naval Institute Press. ISBN0-87021-739-9.
Friedman, Norman (1984). U.S. Cruisers: An Illustrated Design History. Annapolis, Maryland: Naval Institute Press. ISBN0-87021-718-6.
Friedman, Norman (1995). U.S. Submarines Through 1945: An Illustrated Design History. Annapolis, Maryland: Naval Institute Press. ISBN1-55750-263-3.
Gardiner, Robert; Gray, Randal (1985). Conway's All the World's Fighting Ships 1906-1921. London: Conway Maritime Press. ISBN0-85177-245-5.
Grulich, Fred (2004). "Question 37/00: Effectiveness of Shipboard Anti-Aircraft Fire". Warship International. Vol. XLI, no. 1. International Naval Research Organization. pp. 31–33. ISSN0043-0374.
Silverstone, Paul H. (1968). U.S. Warships of World War II. Doubleday and Company.
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