5"/54 caliber Mark 45 gun

The 5-Inch/54-caliber (Mk 45) lightweight gun is a modern U.S. naval artillery gun mount consisting of a 5-inch (127 mm) 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 consist 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.

History
Development started in the 1960s as a replacement for the 5"/54 caliber Mark 42 gun system with a new, lighter, and easier to maintain gun mounting. In USN use, the Mark 45 is used with either the Mk 86 Gun Fire Control System or the Mk 160 Gun Computing System. Since before World War II, 5" has been the standard gun caliber for U.S. Naval ships. Its rate of fire is lower than the British 4.5-inch (113 mm) gun, but it fires a heavier 5" shell which carries a larger burst charge that increases its per-shell effectiveness against aircraft.

Variants

 * Mod 0: used mechanical fuze setter. Two-piece rifled construction, with replaceable liner
 * Mod 1: electronic fuze setter replaces the mechanical one. Made with a unitary construction barrel, which has a life span approximately twice that of the Mark 42 gun.
 * Mod 2: export version of Mod 1, but now used in the US Navy
 * Mod 3: same gun with a new control system; never put into production
 * Mod 4: longer 62-caliber barrel (versus Mod 1 and 2's 54 caliber) for more complete propellant combustion, higher velocity, greater range at +20 NM and thus more utility for land attack.

In sustained firing operations (Mode III), the gun is manned by a six-man crew all located below decks. These are a gun captain, a panel operator, and four ammunition loaders. In fully automatic non-sustained firing operations (Mode IV), the gun can be fired without any personnel inside the mount. However, sustained fire is limited to the capacity of the automatic loader (20 rounds). This means that there will be no one at control panel for the gun to save the weapon when having to fall back to verbal cease fire to the gun crew.
 * Special note:

Users



 * Royal Australian Navy
 * Royal Australian Navy


 * ANZAC-class frigates: Mod 2 being upgraded Mod 4
 * Hobart class destroyer: Mod 4 planned under construction


 * Royal Danish Navy
 * Royal Danish Navy


 * Absalon-class command and support ship command and support ships


 * Hellenic Navy
 * Hellenic Navy


 * Hydra-class frigates (MEKO 200 HN)


 * Japan Maritime Self-Defense Force
 * Japan Maritime Self-Defense Force


 * Atago-class destroyer guided missile destroyers: Mod 4
 * ''Akizuki-class destroyers: Mod 4


 * Republic of Korea Navy
 * Republic of Korea Navy


 * King Sejong the Great-class destroyer guided missile destroyer: Mod 4
 * Chungmugong Yi Sun-sin-class destroyer guided missile destroyer: Mod 4
 * Incheon-class frigate frigate: Mod 4


 * Royal New Zealand Navy: Mod 2
 * Royal New Zealand Navy: Mod 2


 * ANZAC-class frigates


 * Spanish Navy
 * Spanish Navy


 * Álvaro de Bazán-class frigates: Mod 2


 * Republic of China Navy
 * Republic of China Navy


 * Kee Lung-class destroyer guided missile destroyers


 * Royal Thai Navy
 * Royal Thai Navy


 * Naresuan class frigates: Mod 2 being upgraded Mod 4


 * Turkish Navy
 * Turkish Navy


 * Salih Reis-class frigates (MEKO 200 TN II-B)
 * Barbaros-class frigates (MEKO 200 TN II-A)
 * Yavuz-class frigates (MEKO 200 TN)




 * United States Navy
 * Active service ships:
 * Active service ships:


 * Tarawa-class amphibious assault ships (later removed)
 * Ticonderoga-class cruiser guided missile cruisers: Mod 2
 * CG-52: Mod 4 after receiving the cruiser modernization
 * Arleigh Burke-class destroyer guided missile destroyer:
 * DDG 51–80: Mod 2
 * DDG 81–112: Mod 4


 * Decommissioned:


 * California-class cruisers
 * Virginia-class cruisers
 * Kidd-class destroyers
 * Spruance-class destroyers