5-inch/54-caliber Mark 45 gun

History

Development started in the 1960s as a replacement for the 5-inch (127 mm)/54-caliber Mark 42 gun system that had debuted in 1953, with a new, lighter, and easier-to-maintain gun mounting. The United States Navy uses the Mark 45 with either the Mk 86 Gun Fire Control System or the Mk 34 Gun Weapon System.

Since before World War II, 5 inches (127 mm) has been the standard gun caliber for U.S. Naval ships. Its rate of fire is lower than the British 4.5 in gun, but it fires a heavier 5-inch (127 mm) shell which carries a larger burst charge that increases its 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 U.S. Navy.

Mod 3

Mod 2 gun with a new control system. Never put into production.

Mod 4

Receives a longer 62-caliber barrel (versus Mod 1 and 2's 54 caliber) for more complete propellant combustion and higher velocity and thus more utility for land attack. Designed to use the Mark 171 Extended Range Guided Munition (ERGM), which was canceled. 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 operated by a six-person crew: a gun captain, a panel operator, and four ammunition loaders, all located below decks. In fully automatic non-sustained firing operations (Mode IV), 20 rounds can be fired without any personnel inside the mount, using an autoloader.

In 2024–2025, U.S. Navy destroyers in the Red Sea increasingly employed the Mk 45 gun to defend themselves and merchants against one-way attack drones, launched by the Houthi rebels from Yemen.

Ammunition

Mark 68 HE-CVT

• Weight – 68.5 lb (31.1 kg)
• Projectile Length – 26.1 in (66.3 cm)
• Used only with Mods 0–2

Mark 80 HE-PD

• Weight – 67.6 lb (30.7 kg)
• Projectile Length – 26 in (66 cm)
• Explosive filler: 8.2 lb (3.7 kg) Composition B

Mark 91 Illum-MT

• Weight – 63.9 lb (29.0 kg)
• Projectile Length – 26.1 in (66.3 cm)

Mark 116 HE-VT

• Weight – 69.7 lb (31.6 kg)
• Projectile Length – 26 in (66 cm)

Mark 127 HE-CVT

• Weight – 68.6 lb (31.1 kg)
• Projectile Length – 26 in (66 cm)

Mark 156 HE-IR

• Weight – 69.0 lb (31.3 kg)
• Projectile Length – 26 in (66 cm)

Mark 172 HE-ICM (Cargo Round)

• Projectile Length – 26 in (66 cm)
• Used only with Mod 4

Guided shell

In May 2014, the U.S. Navy released a request for information (RFI) for a guided 5-inch (127 mm) round that could be fired from Mark 45 guns on Navy destroyers and cruisers. This RFI came six years after the cancelation 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.

In 2015 Naval Sea Systems Command was 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 was not a program of record . HVP shells fired from 5-inch deck guns would travel at Mach 3, half the speed of attained by a railgun but twice the speed of conventional rounds. The rounds would be more expensive than unguided shells but cheaper than missile interceptors, and engage air and missile targets out to 10-30 nmi.

During 2018 RIMPAC exercises, the fired 20 HVPs from a standard Mk 45 deck gun; an HVP shell could cost US$75,000-$100,000, compared to $1-$2 million for missiles. The cost quoted here is an often-cited reference that continues to grow more stale as annual inflation calculations for Department of Defense are updated during the annual Pentagon Planning-Programming-Budgeting-Execution (PPBE) cycle that generates the annual defense budget request. The annual direction for inflation calculations is provided to the Department of Defense by the White House Office of Management and Budget (OMB) in circular A-11. A review of each fiscal year's inflation adjustment would be required to be applied to the circa 2019 'could cost' estimate noted above to approximate a current cost for procurement.

The HVP was renamed to the Gun-Launched Guided Projectile (GLGP) for the Electromagnetic Railgun project. In 2022, the United States Department of the Navy terminated GLGP Research and Development.

In 2024, the U.S. Navy resumed developmental testing of the Hypervelocity Projectile (HVP) manufactured by BAE Systems USA. The HVP is a saboted round, and is also under development in a U.S. Army contract; the sabot size is larger for the Army version (155mm) but the projectile is common to the HVP developed for the U.S. Navy Mk45 guns, only in a smaller sabot (5"=127mm) for the Navy.

Operators

Current operators

;

• Royal Australian Navy
  • Anzac-class frigate: Mod 2, upgraded Mod 2 versions fitted with a Common Control System.
  • Hobart-class destroyer: Mod 4

;

• Royal Danish Navy
  • Absalon-class frigate: Mod 2

;

• Hellenic Navy
  • Hydra-class frigate (MEKO 200 HN)

;

• Japan Maritime Self-Defense Force
  • Mogami-class frigate: Mod 4
  • Atago-class destroyer: Mod 4
  • Maya-class destroyer: Mod 4
  • Akizuki-class destroyer: Mod 4
  • Asahi-class destroyer: Mod 4

;

• Republic of Korea Navy
  • Sejong the Great-class destroyer: Mod 4
  • Chungmugong Yi Sun-sin-class destroyer: Mod 4
  • Incheon-class frigate: Mod 4

;

• Royal New Zealand Navy
  • Anzac-class frigate: Mod 2

;

• Spanish Navy
  • Álvaro de Bazán-class frigate: Mod 2

;

• Republic of China Navy
  • Kee Lung-class destroyer

;

• Royal Thai Navy
  • Naresuan-class frigate: Mod 2, upgraded to Mod 4

;

• Turkish Navy
  • Barbaros-class frigate (MEKO 200 TN II)
  • Yavuz-class frigate (MEKO 200 TN I)

;

• United States Navy
  • Active service ships:
    • Ticonderoga-class cruiser: Mod 2
      • CG-52-73: Mod 4 after receiving the cruiser modernization
    • Arleigh Burke-class destroyer:
      • DDG 51–80: Mod 2
      • DDG 81–112: Mod 4
  • Decommissioned:
    • California-class cruiser
    • Kidd-class destroyer
    • Spruance-class destroyer
    • Tarawa-class amphibious assault ship (later removed)
    • Virginia-class cruiser
    • (testbed, later removed)

Future operators

;

• Royal Australian Navy
  • *Hunter-*class frigate: 3 ships ordered of 6 planned

;

• Royal Navy
  • Type 26 frigate: 8 ships ordered (Mod 4)

;

• Turkish Navy
  • TF2000-class frigate: 8 ships planned

Cancelled deals

• Indian Navy: The mod 4 variant was planned to be deployed on 7 Nilgiri-class frigate and 4 Visakhapatnam-class destroyer. The procurement of 13 guns was cleared by the Indian Ministry of Defence in April 2018. Of the guns, 11 would be deployed on the above-mentioned ships while 2 would be in the INS Dronacharya missile and gunnery school, and the INS Valsura electrical and weapons engineering school. The US Defense Security Cooperation Agency cleared under the Foreign Military Sales for the same deal in 2019. The deal would be worth over $1 billion. In 2021, India moved on to the development of an indigenous gun of similar calibre due to cost and logistics factor. Till the completion of the development, the 11 destroyers and frigates would be fitted with already operational OTO Melara 76 mm naval gun. The 13 gun deal for the Indian Navy did not go through.

References

Notes

Bibliography

References

1. Norman Polmar, pp. 492–493
2. (18 April 2010). "United States of America 5"/54 (12.7 cm) Mark 45 Mod 4". NavWeaps.Com.
3. (18 September 2007). "United States of America 5"/54 (12.7 cm) Mark 45 Mods 0–2". NavWeaps.Com.
4. (20 February 2009). "The US Navy Fact File: 5-inch Mark 45 54-caliber lightweight gun". United States Navy.
5. "Mk 45 Mod 4 Naval Gun System". [[BAE Systems]].
6. "5-inch 62-Caliber Mk 45 Mod 4 Naval Gun System". BAE Systems.
7. (30 January 2025). "Crew of USS Stockdale Shot Down Houthi Drones with 5-Inch Gun, Says Admiral".
8. [https://www.knds.fr/sites/default/files/2020-05/20180604%20Nexter%20-%20Catalogue%20Ammunition.pdf Ammunition: Nexter Catalogue 2018.]
9. [http://news.usni.org/2014/06/03/navy-taking-second-look-five-inch-guided-round Navy Taking a Second Look at A Five-Inch Guided Round] {{Webarchive. link. (9 June 2014 – News.USNI.org, 3 June 2014)
10. [http://www.navytimes.com/article/20140604/NEWS04/306040080/Navy-seeks-guided-deck-gun-shell Navy seeks guided deck-gun shell] – Navytimes.com, 4 June 2014
11. LaGrone, Sam. (2 June 2015). "Updated: Navy Researching Firing Mach 3 Guided Round from Standard Deck Guns". USNI News.
12. [http://www.popularmechanics.com/military/weapons/a21174/navy-electromagnetic-railgun/ The Future of the Navy's Electromagnetic Railgun Could Be a Big Step Backwards] {{Webarchive. link. (16 July 2016 - Popularmechanics.com, 6 June 2016)
13. [https://news.usni.org/2016/07/18/pentagon-new-rounds-old-guns-change-paradigm-missile-defense-navy-army Pentagon: New Rounds For Old Guns Could Change Missile Defense for Navy, Army] {{Webarchive. link. (19 July 2016 - News.USNI.org, 18 July 2016)
14. [https://news.usni.org/2019/01/08/navy-quietly-fires-20-hyper-velocity-projectiles-destroyers-deckgun Navy Quietly Fires 20 Hyper Velocity Projectiles Through Destroyer's Deckgun] {{Webarchive. link. (9 January 2019 . ''USNI News''. 8 January 2019.)
15. "OMB Circular A-11".
16. (2022-12-21). "USA 5"/62 (12.7 cm) Mark 45 Mod 4".
17. Seck, Hope. (2021-06-04). "It May Be the End of the Line for the Navy's Hypervelocity Projectile".
18. "Highlights of the Department of the Navy FY 2022 Budget".
19. (17 January 2025). "BAE Systems' Hypervelocity Projectile (HVP) at SNA 2025".
20. (27 December 2024). "Army to sole-source deal for hypervelocity projectiles, drone-killing artillery cannon".
21. "BAE to install Mk 45 systems for Navy - Australian Defence Magazine".
22. (2 July 2018). "Australia's Hunter class Type 26 frigates explained". News.com.au.
23. (2018-04-27). "DAC Approves Capital Acquisition Proposals Worth Rs 3,687 Crore".
24. Philip, Snehesh Alex. (2019-11-21). "Ghost of Finmeccanica behind it, Indian Navy to finally get its big guns as US steps in".
25. "Navy to scrap plans to procure guns from US, considering 'Make in India' route now". ThePrint.