View source for 5"/54 caliber Mark 45 gun

{{redirect|5"/54 caliber gun|the earlier 5"/54 gun|5"/54 caliber Mark 42 gun}}
{{redirect|Mark 45|the torpedo|Mark 45 torpedo}}
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{{Infobox Weapon
|name= Mark 45 5-inch/54-caliber lightweight gun
|image=[[File:5-54-Mark-45-firing edit.jpg|300px]]
|caption= 5"/54 Mark 45 mod 2 firing
|origin= [[United States]]
|type= [[Naval gun]]
<!-- Type selection -->
|is_ranged=yes
|is_artillery=yes
<!-- Service history -->
|service=Mark 45 Mod 0: 1971<br />Mark 45 Mod 1: 1980<br />Mark 45 Mod 2: 1988
|used_by=See [[#Users|''users'']]
|wars= 
<!-- Production history -->
|designer= 
|design_date=1968
|manufacturer=[[BAE Systems Land and Armaments]]
|unit_cost=
|production_date=
|number= 
|variants= 
<!-- General specifications -->
|spec_label=
|weight={{convert|21.7|ST|t}}<br />shell: up to 70 lb (32 kg)
|length= 29.5 ft (9 m)
|part_length= 22.5 ft (6.86 m)<br />19.1 ft (5.82 m) (rifling)<br />8,000 rounds (barrel life)
|width=
|height=
|diameter=
|crew=
<!-- Ranged weapon specifications --> 
|cartridge= 
|caliber={{convert|5|in|mm|0}}
|barrels=
|action= 
|rate= 16–20 rounds per minute automatic<ref name="USN facts">{{cite web | url=http://www.navy.mil/navydata/fact_display.asp?cid=2100&tid=575&ct=2 | title=The US Navy -- Fact File | date=2008-01-15}}</ref>
|velocity=2,650 ft/s (808 m/s) full service charge<br />1,500 ft/s (460 m/s) reduced charge for defilade fire or illumination rounds
|range= 13 nautical miles (24 km)
|max_range= 
|feed= 600 rounds (''Ticonderoga'' class)<br />680 rounds (''Arleigh Burke'' class)<br />475–500 rounds (Other classes)
|sights= 
<!-- Artillery specifications -->
|breech=
|recoil=
|carriage=
|elevation=65 / -15 degrees<br />rate: 20 degree/s
|traverse=170 degrees either side of centerline<br />rate: 30 degree/s
}}
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[[File:USS Cowpens (CG-63) firing 5 inch.jpg|thumb|{{USS|Cowpens|CG-63}} fires its Mark 45 mod 2]]
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The '''5-Inch/54-[[Caliber_(artillery)|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. It is designed to be used against surface [[warship]]s, for [[anti-aircraft]] use 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 (below deck) by a three-man crew (gun captain, panel operator, and ammunition loader) to keep the gun supplied with ammunition.  

==History==
Development started in the 1960s as a replacement for the [[5"/54 caliber Mark 42 gun|5-inch/54 Mark 42 gun]] system with a new, lighter, and easier to maintain [[gun mount|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 (114 mm) Mark 8 naval gun|4.5-inch (114 mm) gun]], but it fires a heavier 5" shell, and carries a larger [[burst charge]] which increases its [[Shell (projectile)|per-shell]] effectiveness [[Anti-aircraft warfare|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 barrel (62 [[Caliber_(artillery)|caliber]]s in length versus 54) for more complete propellant combustion, higher velocity and greater utility as a land attack weapon.

;Note:
In sustained firing operations (Mode III), the gun is manned by a three-man crew all located below decks. These are a gun captain, a panel operator, and ammunition loader. 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).

==Users==
;{{USA}}
:[[United States Navy]]
::Active service ships:

* {{sclass|Arleigh Burke|destroyer}} guided missile destroyer:
**DDG 51–80: mod 2<ref name="USN facts"/>
**DDG 81–112: mod 4<ref name="USN facts"/>
* {{sclass|Ticonderoga|cruiser|0}} [[guided missile cruiser]]s: mod 2<ref name="USN facts"/>
**CG-52: mod 4 after receiving the cruiser modernization 
* {{sclass|Tarawa|amphibious assault ship}}s (later removed)

::Decommissioned:
* {{sclass|California|cruiser}}s
* {{sclass|Kidd|destroyer}}s
* {{sclass|Spruance|destroyer}}s
* {{sclass|Virginia|cruiser}}s

;{{AUS}}
:[[Royal Australian Navy]]
[[File:HMAS_Arunta_5inch.jpg|thumb|Mark 45 gun aboard {{HMAS|Arunta|FFH 151}}]]
* {{sclass|ANZAC|frigate}}s
* Australia's intended (in build) [[Hobart class destroyer|''Hobart'' class destroyer]]

;{{DEN}}
:[[Royal Danish Navy]]
* {{sclass|Absalon|command and support ship|0}} command and support ships

;{{GRE}}
:[[Hellenic Navy]]
* {{sclass|Hydra|frigate}}s ([[MEKO]] 200 HN)

;{{JPN}}
:[[Japan Maritime Self-Defense Force]]
* {{sclass|Atago|destroyer|0}} [[guided missile destroyer]]s: mod 4
* {{sclass|5000t|destroyer|0}} [[destroyer]]s: mod 4

;{{ROK}}
:[[Republic of Korea Navy]]
* {{sclass|King Sejong the Great|destroyer|0}} [[guided missile destroyer]]: mod 4
* {{sclass|Chungmugong Yi Sun-sin|destroyer|0}} [[guided missile destroyer]]: mod 4

;{{NZ}}
:[[Royal New Zealand Navy]]
* {{sclass|ANZAC|frigate}}s

;{{ESP}}
:[[Spanish Navy]]
* {{sclass|Álvaro de Bazán|frigate}}s

;{{TWN}}
:[[Republic of China Navy]]
* {{sclass|Kee Lung|destroyer|0}} [[guided missile destroyer]]s

;{{THA}}
:[[Royal Thai Navy]]
*{{sclass|Naresuan|frigate}}s

;{{TUR}}
:[[Turkish Navy]]
* {{sclass|Salih Reis|frigate}}s (MEKO 200 TN II-B)
* {{sclass|Barbaros|frigate}}s (MEKO 200 TN II-A)
* {{sclass|Yavuz|frigate}}s (MEKO 200 TN)

==See also==
{{Commonscat-inline}}
*[[Extended Range Guided Munition]]
*[[4.5 inch (114 mm) Mark 8 naval gun]]: The equivalent gun on British ships, being upgraded to 155&nbsp;mm
*[[Otobreda 127/54 Compact]]: An Italian weapon system, with the same caliber
*[[Advanced Gun System]]—new 155&nbsp;mm long-range gun for the Zumwalt destroyers

==References==
;Notes
{{reflist}}

==External links==
*[http://www.navy.mil/navydata/fact_display.asp?cid=2100&tid=100&ct=2 Navy fact file]
*[http://www.navweaps.com/Weapons/WNUS_5-54_mk45.htm navweaps.com: 5"/54 (12.7 cm) Mark 45 Mods 0 - 2]
*[http://www.fas.org/man/dod-101/navy/docs/swos/gunno/INFO1.html Gunner officer information sheet]

[[Category:127 mm artillery]]
[[Category:Naval guns of the United States]]
[[Category:Cold War naval weapons]]
[[Category:Naval anti-aircraft guns|5 inch]]

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