12"/45 caliber Mark 5 gun

The 12″/45 caliber Mark 5 gun was an American naval gun that first entered service in 1906. Initially designed for use with the Connecticut-class of pre-dreadnought battleships, the Mark 5 continued in service aboard the first generation of American dreadnoughts.

12″/45 caliber Mark 5 Naval Gun
12-45 mk5 Connecticut gun pic
Mark 5 gun being hoisted aboard USS Connecticut
TypeNaval gun
Coastal defence
Place of originUnited States
Service history
In service1906–1930
Used by
  • United States Navy
  • Greek Navy
Production history
DesignerBureau of Ordnance
ManufacturerU.S. Naval Gun Factory[2]
Mass53 short tons (48 t)
Barrel length45 ft 0 in (13.72 m) bore (45 calibers)

Shell870 lb (390 kg)
Caliber12 in (305 mm)
Elevation-5° to +15°
Rate of fire2–3 rpm
Muzzle velocity2,700 ft/s (820 m/s)
Effective firing range20,000 yd (18,288 m) at 15° elevation
30,000 yd (27,432 m) at 47° elevation As coastal artillery

Design and development

The 12-inch (305 mm)/45 caliber Mark 5 naval gun was designed as an incremental improvement upon the preceding American naval gun, the 12"/40 caliber gun Mark 4.[1] As such, it was a very similar weapon, having been lengthened by 5 calibers to allow for improved muzzle velocity, range, and penetrating power. Designed to the specifications of the Bureau of Ordnance, the Mark 5 was constructed at the U.S. Naval Gun Factory in Washington, D.C.[2]

Measurements and Capabilities

The Mark 5 weighed 53 short tons (48 t) and was capable of firing 2 to 3 times a minute. At maximum elevation of 15° it could fire an 870 lb (390 kg) shell approximately 20,000 yd (18,000 m). However, this range was largely academic at the time the gun was initially designed, as no rangefinding techniques had yet been developed capable of accurately firing beyond about 10,000 yd (9,100 m). With an initial muzzle velocity of 2,700 ft/s (820 m/s), the gun had a barrel life of 175 rounds, and was capable of firing either Armor Piercing or Common projectiles.[1][3]

As designed, the Mark 5 was capable of penetrating 16.6 in (420 mm) of Harvey plated side armor at 6,000 yd (5,500 m), 12.2 in (310 mm) at 9,000 yd (8,200 m), and 9.9 in (250 mm) at 12,000 yd (11,000 m). By comparison the 12-inch/40 caliber Mark 4 it replaced could only penetrate 14.6 in (370 mm), 11.6 in (290 mm), and 9.4 in (240 mm) at those distances, respectively.[1]

Naval Service

USS Delaware (BB-28) - NH 54666
After six Mark 5 guns aboard USS Delaware, c. 1913.

The Mark 5 entered service in 1906 and remained the primary battleship gun for all American battleships commissioned before 1912, at which point it was replaced by the 12"/50 caliber Mark 7.[1] All told, the Mark 5 would arm 14 battleships of five different classes, making it the most-utilized main gun in American battleship history. Despite this distinction, the only Mark 5 guns ever to be fired in anger were actually in Greek, and not American, service. The ex-Mississippi-class battleships Kilkis and Lemnos, sold to the Royal Hellenic Navy in 1914, fought in both the Allied Intervention in the Russian Civil War, and the Greco-Turkish War.[4] Though during World War I the Mark 5 would cross the Atlantic for duty aboard two of the American battleships serving in the 6th Battle Squadron of the Grand Fleet, it was never fired in any engagement, as no battles were fought with the German High Seas Fleet in 1918.

The five classes armed with the Mark 5 were:

In American service, the Mark 5 remained afloat (albeit in dwindling numbers) until 1930, when the last guns were removed from the Floridas in compliance with the terms of the London Naval Treaty.[5]


A Mark 5 Mod 8 gun is displayed at Fort Hamilton in Brooklyn, New York, representative of the general type of coast artillery guns the fort had.


USS Michigan blown off 12 inch gun
View looking aft along the port side, showing barrel of burst 12-inch gun on deck with the gun's rear portion in Turret # 2. Photographed at the Philadelphia Navy Yard, Pennsylvania, 25 September 1916. Note holes in superstructure and in the "cage" foremast caused by this accident.

During the summer of 1916, Michigan blew out her left hand gun in turret No. 2 during target practice. After an investigation of South Carolina's guns it was discovered that copper deposits from the driving bands on the projectiles had narrowed the bores of the barrel enough that it caused the projectiles to slow down. This problem, known as "copper choke", allowed the pressure in the barrel to increase to dangerous levels. Lapping heads, to remove these deposits, were issued for all guns 12-inch and larger throughout the fleet.[1] The lapping heads were later replaced by wire and pisaba brushes.[6][1]

Coastal Artillery

Following the signing of the Washington Naval Treaty in 1922, many of the Mark 5 guns in service were removed from sea duty and transferred to the U.S. Army for use as coastal artillery. In this capacity, the maximum range of the Mark 5 increased to 30,000 yd (27,000 m), due to the greater elevation that was possible. These guns were not deployed by the US Army, and some were sold to Brazil, where they might still be in use.[1][7] In Greek service, the guns removed from Lemnos were emplaced on the island of Aegina, where they helped to defend the approaches to the port of Athens.[4]

See also

Weapons of comparable role, performance and era


  1. ^ a b c d e f g h DiGiulian, Tony (11 April 2016). "USA 12"/45 (30.5cm) Mark 5 and Mark 6". Navweaps.com. Archived from the original on 19 February 2009. Retrieved 18 October 2016.
  2. ^ a b "Washington Navy Yard: History of the Naval Gun Factory, 1883-1939". history.navy.mil. Retrieved 8 November 2015.
  3. ^ Friedman (1978), p. 153.
  4. ^ a b "Greek Navy Ships -- Lemnos". Naval Historical Center. 27 March 2001. Retrieved 17 November 2009.
  5. ^ "BB-30 Florida Class". globalsecurity.org. 27 April 2005. Archived from the original on 16 February 2009. Retrieved 11 February 2009.
  6. ^ "Definitions and Information about Naval Guns Part 3 - Miscellaneous Definitions". Navweaps. 7 May 2016. Retrieved 18 October 2016.
  7. ^ "Coastal Defence Forces (Brazil)". janes.com. 13 August 2008. Archived from the original on 24 February 2009. Retrieved 13 February 2009.

External links

12"/40 caliber gun

The 12"/40 caliber gun (spoken as "twelve-inch-forty--caliber") were used for the primary batteries of the United States Navy's last class of monitors and the Maine-class and Virginia-class pre-dreadnought battleships.

12"/50 caliber Mark 7 gun

The 12"/50 caliber Mark 7 gun (spoken "twelve-inch-fifty-caliber") was a United States Navy's naval gun that first entered service in 1912. Initially designed for use with the Wyoming-class of dreadnought battleships, the Mark 7 also armed the Argentine Navy's Rivadavia-class battleships.

14"/45 caliber gun

The 14"/45 caliber gun, (spoken "fourteen-inch-forty-five-caliber"), whose variations were known initially as the Mark 1, 2, 3, and 5, and, when upgraded in the 1930s, were redesignated as the Mark 8, 9, 10, and 12. They were the first 14-inch (356 mm) guns to be employed with the United States Navy and were, for over a year, the most powerful naval ordnance afloat. The 14-inch/45 caliber guns were installed as the primary armament aboard all of the United States Navy's New York-class, Nevada-class, and Pennsylvania-class battleships. The gun also saw service in the British Royal Navy, where it was designated the BL 14 inch gun Mk II.

14"/50 caliber gun

The 14"/50 caliber gun was a naval gun mounted on New Mexico and Tennessee-class battleships. These ships also featured the first "three-gun" turrets, meaning that each gun in each turret could be "individually sleeved" to elevate separately (however, they could be linked so they would elevate as a unit, similar to the triple turrets on other Navy ships). The 14"/50 caliber guns were designated as Mark 4 and 6, with later versions known as Mark 7, 11, and B. These guns were more powerful than the main gun mounted on the previous three classes of US battleships (the New York, Nevada and Pennsylvania classes), the 14"/45 caliber gun.

16"/45 caliber Mark 6 gun

The 16"/45 caliber Mark 6 gun is a naval gun designed in 1936 by the United States Navy for their Treaty battleships. It was first introduced in 1941 aboard their North Carolina-class battleships, replacing the originally intended 14"/50 caliber Mark B guns and was also used for the follow-up South Dakota class. These battleships carried nine guns in three three-gun turrets. The gun was an improvement to the 16"/45 caliber guns used aboard the Colorado class, and the predecessor to the 16"/50 caliber Mark 7 gun used aboard the Iowa class.

16"/45 caliber gun

The 16"/45 caliber gun (spoken "sixteen-inch-forty-five-caliber") was used for the main batteries of the last class of Standard-type battleships for the United States Navy, the Colorado-class. These guns promised twice the muzzle energy over the Mark 7 12-inch/50 caliber guns of the Wyoming-class battleship and a 50% increase over the 14-inch/45 caliber guns of the New York-class, Nevada-class, and Pennsylvania-class battleships.

3"/23 caliber gun

The 3"/23 caliber gun (spoken "three-inch-twenty-three-caliber") was the standard anti-aircraft gun for United States destroyers through World War I and the 1920s. United States naval gun terminology indicates the gun fired a projectile 3 inches (76 mm) in diameter, and the barrel was 23 calibers long (barrel length is 3" x 23 = 69" or 1.75 meters.)

3"/50 caliber gun

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 1890 through the 1990s on a variety of combatant and transport ship classes.

The gun is still in use with the Spanish Navy on Serviola-class patrol boats.

4"/50 caliber gun

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5"/40 caliber gun

The 5"/40 caliber gun (spoken "five-inch-forty-caliber") were used in the secondary batteries of the United States Navy's early battleships, armored cruisers, protected cruisers, unprotected cruisers, and auxiliary cruisers.

5"/51 caliber gun

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.

5"/54 caliber Mark 45 gun

The 5-inch/54 caliber (Mk 45) lightweight gun is a U.S. naval artillery gun mount consisting of a 127 mm (5 in) L54 Mark 19 gun on the Mark 45 mount. Originally designed and built by United Defense, it is now manufactured by BAE Systems Land & Armaments after the former was acquired.

The latest 5-inch/62 caliber version consists of a longer barrel L62 Mark 36 gun fitted on the same Mark 45 mount. The gun is designed for use against surface warships, anti-aircraft and shore bombardment to support amphibious operations. The gun mount features an automatic loader with a capacity of 20 rounds. These can be fired under full automatic control, taking a little over a minute to exhaust those rounds at maximum fire rate. For sustained use, the gun mount would be occupied by a six-man crew (gun captain, panel operator, and four ammunition loaders) below deck to keep the gun continuously supplied with ammunition.

6"/50 caliber gun

The 6"/50 caliber gun Mark 6 and Mark 8 (spoken "six-inch-fifty-caliber") were used for the secondary batteries of the United States Navy's Maine-class and Virginia-class battleships, as well as the Pennsylvania-class and Tennessee-class armored cruisers. They were also used as the main battery on the St. Louis-class protected cruisers.

7"/44 caliber gun

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8"/35 caliber gun

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8"/45 caliber gun

The 8"/45 caliber Mark 6 gun (spoken "eight-inch-forty-five--caliber") were used for the secondary batteries of the United States Navy's last pre-dreadnought battleships and refitted in older armored cruisers main batteries.

Dual-purpose gun

A dual-purpose gun is a naval artillery mounting designed to engage both surface and air targets.

QF 12-pounder 12 cwt naval gun

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As the Type 41 3-inch (76.2 mm)/40 it was used on most early battleships and cruisers of the Imperial Japanese Navy, though it was commonly referred to by its UK designation as a "12-pounder" gun.

QF 4.7-inch Mk I – IV naval gun

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The gun was originally designed to replace the older BL 5-inch (127 mm) naval guns. It was optimised for the modern smokeless propellants, such as Cordite, and could be loaded and fired far more rapidly than the BL 5-inch gun while firing a shell only slightly lighter.

American naval weapons of the First World War
Capital ship main armament
Cruiser main armament
Secondary armament
Destroyer and gunboat armament
Submarine guns
Anti-aircraft weapons
Light weapons
Anti-submarine weapons

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