5"/51 caliber gun
5"/51 caliber Mark 8 gun on starboard forecastle of
, March 1914
Place of origin United States Service history In service 1911– c. 1947 Used by
Production history Designer Bureau of Ordnance Designed 1910 Manufacturer
Mark 7: 93 (Nos. 357–449)
Mark 8: 1004 (NGF 539 Nos. 450-unknown)(see builders)
(No Nos. 1357–1456, 1519–1604 or 1633–1704) Mark 9: 3 (Unknown Nos.)
Mark 14: relined Mark 8s
Mark 15: enlarged chamber Mark 14s Variants Marks 7, 8, 9, 14, 15 Specifications Weight
Mark 7: 11,274 lb (5,114 kg) (with breech)
Mark 8: 10,834 lb (4,914 kg) (without breech)
Mark 8: 11,300 lb (5,100 kg) (with breech)
Mark 9: 10,824 lb (4,910 kg) (without breech)
Mark 9: 11,375 lb (5,160 kg) (with breech) Length 261.25 in (6,636 mm) Barrel length 255 in (6,500 mm) bore (51 calibers) Shell 50–55.18 lb (22.68–25.03 kg) Caliber 5 in (127 mm) Breech side swing Welin-type Elevation
P13: -10° to +20° (late version)
P15: -15° to +20°
Mark 18: -8.5° to +25° Traverse up to 360° depending on location Rate of fire 8-9 rounds per minute Muzzle velocity
3,150 ft/s (960 m/s) (full charge)
2,300 ft/s (700 m/s) (reduced charge) Effective firing range 17,000 yd (16,000 m) at 20° elevation Maximum firing range 20,142 yd (18,418 m) at 45° elevation (World War II ammunition)
5"/51 caliber guns (spoken "five-inch-fifty-one-caliber") initially served as the secondary battery of United States Navy battleships built from 1907 through the 1920s, also serving on other vessels. United States naval gun terminology indicates the gun fired a projectile 5-inch (127 mm) in diameter, and the barrel was 51 calibers long.
The different marks of the gun were Marks 7, 8, 9, 14, and 15. The
built-up gun consisted of a tube, full-length jacket, and single hoop with side swing Welin breech block and Smith- Asbury mechanism for a total weight of about 5 metric tons. Some Marks included a tapered liner. A 24.5 lb (11.1 kg) charge of smokeless powder gave a 50-pound (23 kg) projectile a velocity of 3,150 ft/s (960 m/s). Range was 15,850 yards (9.0 statute miles or 14.5 kilometres) at the maximum elevation of 20 degrees. Useful life expectancy was 900  effective full charges (EFC) per liner.
On a US Navy transport ship c. mid 1942
The 5-inch/51 caliber gun was designed to engage destroyers, torpedo boats, and other surface targets. It entered service in 1911 as secondary armament on the
Florida-class battleships, with many of the guns being removed soon after commission because they were too wet. Most of the remaining guns were moved to redesigned casemates during the 1927–1930 refits. Increased awareness of the need for anti-aircraft protection (especially following the attack on Pearl Harbor) encouraged mounting of dual-purpose 5"/38 caliber guns in later battleships, and some of the World War I-era battleships were rearmed with 5"/38 caliber guns during World War II. Surplus guns from scrapped or disarmed battleships were mounted in United States Coast Guard cutters, auxiliaries, small aircraft carriers, coast defense batteries, and Defensively Equipped Merchant Ships. A 1939 Table of Organization and Equipment shows  Marine defense battalions were equipped with six of these guns each. 5-inch/51 shore batteries were used with great effectiveness by the  1st Marine Defense Battalion during the Battle of Wake Island in December 1941. These were replaced in the defense battalions by the 155 mm Long Tom gun by 1943. Six were rearmed with "wet mount" 5-inch/51 guns during World War II, taken from Tambor-class submarines submarines or spares for that class.
The 5"/51 caliber gun was mounted on:
Army coast defense use
5"/51 caliber ex-Navy guns were emplaced during World War II at several locations, some operated by the
United States Army Coast Artillery Corps and some by Marine defense battalions. This list may not be exhaustive. They were grouped into two-gun batteries unless otherwise noted.
Two guns near Cape Lookout, NC
Three guns in Battery Gillespie, Point Loma, San Diego, CA
Three guns in Battery Ahua,
Fort Kamehameha, Oahu, HI Two guns in Battery Nanakuli, Oahu, HI
Two guns in Battery Oneula (Ewa), Oahu, HI
Two guns at Kahana Bay, North Shore, Oahu, HI
In British service these guns were known as 5"/51 BL Mark VI and Mark VII. During World War I three of these guns formed part of the coastal defences of Scapa Flow.
In World War II a small number of these guns entered British service on board ships transferred under the  Lend-Lease arrangement. Some of these guns were then transferred to New Zealand (at least six, possibly more) and deployed ashore for coastal defence.
Surviving 5"/51 caliber guns include:
Eight guns on
USS , preserved at the Olympia (C-6) Independence Seaport Museum in Philadelphia, Pennsylvania (guns previously on USS ) Colorado (BB-45) Six guns preserved on
USS near Houston, Texas Texas (BB-35) One Mark 8 gun (Four Lakes #1205) at
Trumbo Point, Key West, Florida (part of Naval Air Station Key West) One gun (Unk. mfr. #1093L2) at the
Ropkey Armor Museum, Crawfordsville, Indiana (previously on USS and allegedly on Arizona (BB-39) USS or Indiana (BB-1) USS at some time) Indiana (BB-58) Two Mark 7 guns (
Watervliet #774 and #Unk.) on Midway Island, Central Pacific Ocean One Mark 7 gun (
Naval Gun Factory (NGF) #415L) at the NROTC facility, Tulane University, New Orleans, Louisiana One Mark 15 gun (NGF #736L) at the
U.S. Navy Museum, Washington Navy Yard, Washington, DC (previously on USS ) Idaho (BB-42) One 5"/51 caliber gun at
Fort Schuyler, Bronx, New York (possibly at USMMA, Kings Point, New York) One 5"/51 caliber gun at
Treasure Island, San Francisco, California (behind museum) One Mark 15 gun in
Lewiston, Maine One Mark 15 gun (
Bethlehem #Unk.) at the Brunswick Executive Airport, Brunswick, Maine (formerly NAS Brunswick) One 5"/51 caliber gun in
Mitchell, Indiana One Mark 9 Mod 3 gun (NGF #938L),
American Military Museum, South El Monte, California One 5"/51 caliber gun at the Veterans Memorial Museum, Chehalis, WA
^ Fairfield 1921 p. 156
^ a b c DiGiulian, Tony,
"United States of America 5"/51 (12.7 cm) Marks 7, 8, 9, 14 and 15. British 5"/51 (12.7 cm) BL Marks VI and VII
^ a b Campbell 1985 p.136
^ Bogart, Charles H., "Fifth Marine Defense Battalion in Iceland",
Coast Defense Journal, Vol. 29, Issue 3, August 2015, Coast Defense Study Group, Inc.
^ Bauer and Roberts, p. 144
^ a b c Preston 1980 p. 60
^ a b Breyer 1973 p. 201
^ a b Breyer 1973 p. 202
^ a b Breyer 1973 p. 205
^ a b Friedman 2011 p. 185
^ a b Breyer 1973 p. 210
^ a b Breyer 1973 p. 214
^ a b c Breyer 1973 p. 219
^ a b Breyer 1973 p. 226
^ a b c Breyer 1973 p. 230
^ Bauer and Roberts, pp. 178-179
^ a b Fahey 1939 p. 18
^ Bauer and Roberts, p. 265
^ Fahey 1939 p. 7
^ Friedman 1983 p. 162
^ a b c d Friedman 1983 p. 407
^ Friedman 1983 p. 164
^ Friedman 1983 p. 170
^ a b c Fahey 1941 p. 42
^ Berhow, pp. 238-239
Bauer, K. Jack; Roberts, Stephen S. (1991). Register of Ships of the U.S. Navy, 1775-1990: Major Combatants. Westport, Connecticut: Greenwood Press. ISBN 0-313-26202-0.
Berhow, Mark A., Ed. (2015). American Seacoast Defenses, A Reference Guide, Third Edition. McLean, Virginia: CDSG Press. ISBN 978-0-9748167-3-9.
Breyer, Siegfried (1973). Battleships and Battlecruisers 1905–1970. Doubleday and Company. ISBN 0-385-07247-3.
Campbell, John (1985). Naval Weapons of World War Two. Naval Institute Press. ISBN 0-87021-459-4.
Fahey, James C. (1939). The Ships and Aircraft of the U.S. Fleet. Ships and Aircraft.
Fahey, James C. (1941). The Ships and Aircraft of the U.S. Fleet, Two-Ocean Fleet Edition. Ships and Aircraft.
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Friedman, Norman (1983). U.S. Aircraft Carriers. Naval Institute Press. ISBN 0-87021-739-9.
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