5"/54 caliber Mark 45 gun

The 127 mm (5")/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.[1] Originally designed and built by United Defense, it is now manufactured by BAE Systems Land & Armaments after the former was acquired.

Mark 45 5-inch/54-caliber lightweight gun
The latest version, a 5-inch/62 caliber Mark 45 Mod 4, in flat-panel gun turret, test firing on USS Forrest Sherman in 2007
TypeNaval gun
Place of originUnited States
Service history
In service1971-present
Used bySee Operators
Production history
ManufacturerUnited Defense[1] (now BAE Systems Land & Armaments)
Specifications (Mod 2)
Mass21,691 kg (47,820.5 lb)[1]
Length8.992 m (29 ft 6.0 in)[3]
Barrel length6.858 m (270.0 in)[3]
Rifling: 5.82 m (229 in)[3]

ShellConventional: 31.75 kg (70.0 lb)[1]
Caliber5.0 inches (127.0 mm)
BarrelsSingle barrel (progressive RH parabolic twist)
  • −15° to +65°[3]
  • Max. elevation rate: 20°/s[3]
  • ±170° from centerline[3]
  • Max. traversing rate: 30°/s[3]
Rate of fire16–20 rounds per minute automatic[4]
Muzzle velocity
  • 2,500 ft/s (762.0 m/s)[1]
  • 1,500 ft/s (457.2 m/s) reduced charge for defilade fire or illumination rounds
Effective firing range13 nmi (24.1 km)[4]
Feed system
  • 600 rounds (Ticonderoga class)
  • 680 rounds (Arleigh Burke class)
  • 475–500 rounds (other classes)

The latest 127 mm (5")/62 caliber version consists of a longer barrel L62 Mark 36 gun fitted on the same Mark 45 mount.[1] The gun is designed for use against surface warships, anti-aircraft and shore bombardment to support amphibious operations.[1] 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.


Development started in the 1960s as a replacement for the 127 mm (5")/54 caliber Mark 42 gun system that had debuted in 1953 with a new, lighter, and easier to maintain gun mounting. In United States Navy 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, 127 mm (5 inches) has been the standard gun caliber for U.S. Naval ships. Its rate of fire is lower than the British 4.5 in (114 mm) gun, but it fires a heavier 127 mm (5-inch) shell which carries a larger burst charge that increases its per-shell effectiveness against aircraft.


  • 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 and higher velocity[5] and thus more utility for land attack. Additionally, the Mk 45 mod 4 uses a modified flat-panel gun turret, designed to reduce its radar signature.

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).

Guided shell

On 9 May 2014, the U.S. Navy released a request for information (RFI) for a guided 127 mm (5-inch) round that could be fired from Mark 45 guns on Navy destroyers and cruisers. The thinking is that if the technology worked in the 155 mm (6 in) Long Range Land Attack Projectile (LRLAP) for the Advanced Gun System on Zumwalt-class destroyers, it can be applied to a 127 mm (5-inch) mount. This RFI comes six years after the cancellation of the Raytheon Extended Range Guided Munition. The shell must have at least double the range of unguided shells for missions including Naval Surface Fire Support (NSFS)/Land Attack, and increasing anti-surface warfare (ASuW) capabilities against fast attack craft (FAC) and fast inshore attack craft (FIAC); the main purpose is to destroy incoming small boats at a greater range with a proximity fuse airburst blast fragmentation warhead to spray shrapnel over swarms. Expected submissions include the BAE Systems Multi Service–Standard Guided Projectile (MS-SGP), Raytheon Excalibur N5, and OTO Melara Vulcano guided long-range projectile.[6][7]

Naval Sea Systems Command is also looking to fire a version of the hyper velocity projectile (HVP) developed for Navy electromagnetic railguns from conventional 5-inch deck guns. Using the HVP could give existing destroyers and cruisers better ability to engage land, air, and missile threats and allow more time to refine the railgun. The HVP would be a cheaper solution to intercepting incoming missiles than a missile interceptor costing hundreds of thousands of dollars. Converting the HVP to fire from conventional guns is not yet a program of record.[8] HVP shells fired from 5-inch deck guns would travel at Mach 3, half the speed of a railgun but twice the speed of conventional rounds.[9] The rounds would be more expensive than unguided shells but cheaper than missile interceptors, and engage air and missile targets out to 10–30 nautical miles (12–35 mi; 19–56 km).[10] During 2018 RIMPAC exercises, the USS Dewey (DDG-105) fired 20 HVPs from a standard Mk 45 deck gun; an HVP shell could cost $75,000-$100,000, compared to $1-$2 million for missiles.[11]


Current operators

Royal Australian Navy
Royal Danish Navy
Hellenic Navy
Japan Maritime Self-Defense Force
 South Korea
Republic of Korea Navy
 New Zealand
Royal New Zealand Navy
Spanish Navy
Republic of China Navy
Royal Thai Navy
Turkish Navy
 United States
United States Navy
Active service ships:

Future operators

Royal Australian Navy
Royal Canadian Navy
 United Kingdom
Royal Navy
Indian Navy

See also

Weapons of comparable role, performance and era



  1. Norman Polmar, pp. 492–493
  2. "United States of America 5"/54 (12.7 cm) Mark 45 Mod 4". NavWeaps.Com. 18 April 2010. Archived from the original on 2 January 2015. Retrieved 24 October 2010.
  3. "United States of America 5"/54 (12.7 cm) Mark 45 Mods 0–2". NavWeaps.Com. 18 September 2007. Archived from the original on 3 January 2015. Retrieved 24 October 2010.
  4. "The US Navy Fact File: 5-inch Mark 45 54-caliber lightweight gun". United States Navy. 20 February 2009. Archived from the original on 5 December 2010. Retrieved 24 October 2010.
  5. "5-inch 62-Caliber Mk 45 Mod 4 Naval Gun System" (PDF). Brochure. BAE Systems. Archived from the original (PDF) on 25 April 2012. Retrieved 5 October 2011.
  6. Navy Taking a Second Look at A Five-Inch Guided Round Archived 9 June 2014 at the Wayback Machine – News.USNI.org, 3 June 2014
  7. Navy seeks guided deck-gun shell – Navytimes.com, 4 June 2014
  8. Navy Researching Firing Mach 3 Guided Round from Standard Deck Guns Archived 1 June 2015 at the Wayback Machine – News.USNI.org, 1 June 2015
  9. The Future of the Navy's Electromagnetic Railgun Could Be a Big Step Backwards Archived 16 July 2016 at the Wayback Machine - Popularmechanics.com, 6 June 2016
  10. Pentagon: New Rounds For Old Guns Could Change Missile Defense for Navy, Army Archived 19 July 2016 at the Wayback Machine - News.USNI.org, 18 July 2016
  11. Navy Quietly Fires 20 Hyper Velocity Projectiles Through Destroyer’s Deckgun Archived 9 January 2019 at the Wayback Machine. USNI News. 8 January 2019.
  12. "Australia's Hunter class Type 26 frigates explained". news.com.au. Archived from the original on 1 March 2019. Retrieved 18 March 2019.
  13. "Ottawa awards design contract for $60-billion warship fleet to Lockheed Martin". CTV News. Archived from the original on 9 February 2019. Retrieved 11 February 2019. 8 February 2019.
  14. "Trump Administration approves sale of $1 billion worth of naval guns to India". LiveMint. Retrieved 20 November 2019.


  • Norman, Polmar (2005). The Naval Institute guide to the ships and aircraft of the U.S. fleet (18th ed.). Annapolis, MD: Naval Institute Press. pp. 492–493. ISBN 978-1-59114-685-8.

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