8-inch/55-caliber gun



The 8"/55 caliber gun (spoken "eight-inch-fifty-five-caliber") formed the main battery of United States Navy heavy cruisers and two early aircraft carriers. United States naval gun terminology indicates the gun barrel had an internal diameter of 8 inches (203 mm), and the barrel was 55 calibers long (barrel length is 8 inch × 55 = 440 inches or 36.6 feet or 11 meters).

Mark 9
These built-up guns weighed about 30 tons including a liner, tube, jacket, and five hoops. A down-swing Welin breech block was closed by compressed air from the gas ejector system. Loading with two silk bags each containing 45 lb of smokeless powder gave a 260 lb projectile a velocity of 2800 feet per second (853 m/s). Range was 18 miles 31860 yd at the maximum elevation of 41 degrees.

Mark 12
These simplified built-up guns eliminated hoops to reduce weight to 17 tons. The breech mechanism was similar and loading two silk bags each containing 43 pounds (20 kg) of smokeless powder gave a 335-pound (152 kg) projectile a velocity of 2500 feet per second (760 m/s). Each gun could fire about four rounds per minute. Maximum range was 30050 yd at the maximum elevation of 41 degrees.

Mark 14
These guns were similar to Mark 9, with the same shell weight and maximum range, with a smaller chamber and rifling twist increased from 1 in 35 to 1 in 25 in a chromium-plated bore.

Mark 15
These guns were similar to Mark 12, with the same shell weight and maximum range, with the smaller chamber of the Mark 14 gun. Useful life expectancy was 715 effective full charges (EFC) per liner.

Mark 16
These self-loading guns with lined monobloc construction and vertical sliding breech blocks weighed about 20 tons. Semi-fixed ammunition (projectile and powder case handled separately) with 78 pounds (35 kg) of smokeless powder gave a 335-pound (152 kg) projectile a velocity of 2500 feet per second (760 m/s). Each gun could fire about ten rounds per minute. Useful life expectancy was 780 Effective Full Charges per liner. Range was 17 miles (27 kilometers) at the maximum elevation of 41 degrees. This gun was modified for the experimental Major Caliber Lightweight Gun.

Coast defense use
The eight twin turrets of USS Lexington (CV-2) and USS Saratoga (CV-3) were removed in early 1942 during refits at Pearl Harbor. The turrets were turned over to the United States Army Coast Artillery Corps and remounted as coastal artillery on Oahu. Four two-turret batteries were established at Salt Lake near Aliamanu Crater (Battery Salt Lake, later Battery Burgess), Wiliwilinui Ridge Military Reservation (Battery Wilridge, later Battery Kirkpatrick), Opaeula Military Reservation (Battery Opaeula, later Battery Riggs), and Brodie Camp Military Reservation (Battery Brodie, later Battery George Ricker). After the war, all of the guns and turrets were scrapped in 1948, along with almost all other US coast artillery.

One of USS Louisville (CA-28)'s main battery 8 inch 55 caliber gun turrets (Turret No. 2) damaged in a kamikaze attack on January 5, 1945, was removed and taken to the Nevada Test Site and converted into a rotating radiation detector, to collect data on nuclear tests.

Ships mounting 8"/55 caliber guns



 * 2 Lexington-class aircraft carrier (c. 1921 – 1925) aircraft carriers:
 * USS Lexington (CV-2), USS Saratoga (CV-3)
 * Mk 9 guns in four 190-ton twin turrets
 * removed in 1942 and added to Oahu coast defenses
 * 2 Pensacola-class cruiser (c. 1927) heavy cruisers:
 * USS Pensacola (CA-24), USS Salt Lake City (CA-25)
 * Mk 9 (later Mk 14) guns in two 190-ton twin turrets and two 250-ton triple turrets
 * 6 Northampton-class cruiser (c. 1928) heavy cruisers:
 * 2 of 6: USS Chicago (CA-29), USS Houston (CA-30)
 * Mk 9 guns in three 250-ton triple turrets
 * Houston was sunk in March 1942, Chicago was sunk in January 1943
 * 4 of 6: USS Northampton (CA-26), USS Chester (CA-27), USS Louisville (CA-28), USS Augusta (CA-31)
 * Mk 9 (later Mk 14) guns in three 250-ton triple turrets
 * 2 Portland-class cruiser (c. 1930) heavy cruisers:
 * USS Portland (CA-33), USS Indianapolis (CA-35)
 * Mk 9 (later Mk 14) guns in three 250-ton triple turrets
 * 7 New Orleans-class cruiser (c. 1931) heavy cruisers:
 * 3 of 7: 294 ton triple turrets
 * USS Astoria (CA-34): Mk 9 guns (sunk in 08/1942)
 * USS New Orleans (CA-32): Mk 9 (later Mk 14) guns
 * USS Minneapolis (CA-36): Mk 9 (later Mk 15) guns
 * 4 of 7: USS Tuscaloosa (CA-37), USS San Francisco (CA-38), USS Quincy (CA-39), USS Vincennes (CA-44)
 * Mk 12 guns in three 250-ton triple turrets
 * USS Wichita (CA-45)
 * Mk 12 guns in three 314-ton triple turrets
 * 14 Baltimore-class cruiser (c. 1941) heavy cruisers:
 * 1 of 14: USS Baltimore (CA-68)
 * Mk 12 guns in three 300-ton triple turrets
 * 13 of 14: USS Boston (CA-69), USS Canberra (CA-70), USS Quincy (CA-71), USS Pittsburgh (CA-72), USS Saint Paul (CA-73), USS Columbus (CA-74), USS Helena (CA-75), USS Bremerton (CA-130), USS Fall River (CA-131), USS Macon (CA-132), USS Toledo (CA-133), USS Los Angeles (CA-135), USS Chicago (CA-136)
 * Mk 15 guns in three 300-ton triple turrets
 * 3 Oregon City-class cruiser (c. 1944) heavy cruisers:
 * USS Oregon City (CA-122), USS Albany (CA-123), USS Rochester (CA-124)
 * Mk 15 guns in three 300-ton triple turrets
 * 3 Des Moines-class cruiser (c. 1945) heavy cruisers:
 * USS Des Moines (CA-134), USS Salem (CA-139), USS Newport News (CA-148)
 * Mk 16 guns in three 450-ton triple turrets
 * 1 ex-Forrest Sherman-class destroyer: USS Hull (DD-945)
 * Mk 16 gun in one 86-ton single automatic mount 8"/55 caliber Mark 71 gun installation

Weapons of comparable role, performance and era

 * 203mm/50 Modèle 1924 gun French equivalent
 * 20.3 cm SK C/34 Naval gun German equivalent
 * 203 mm /53 Italian naval gun Italian equivalent
 * 20 cm/50 3rd Year Type naval gun Japanese equivalent
 * BL 8 inch Mk VIII naval gun UK equivalent