5"/54 caliber Mark 45 gun

Mark 45 5-inch/54-caliber lightweight gun
Mark 45 5-inch/54-caliber lightweight gun
	300px; 5"/54 Mark 45 mod 2 firing
Type	Naval gun
Place of origin	United States
Service history
In service	Mark 45 Mod 0: 1971; Mark 45 Mod 1: 1980; Mark 45 Mod 2: 1988
Used by	See users
Production history
Designed	1968
Manufacturer	BAE Systems Land and Armaments
Specifications
Weight	21.7 short tons (19.7 t); shell: up to 70 lb (32 kg)
Length	29.5 ft (9 m)
Barrel length	22.5 ft (6.86 m); 19.1 ft (5.82 m) (rifling); 8,000 rounds (barrel life)
Caliber	5 inches (127 mm)
Elevation	65 / -15 degrees; rate: 20 degree/s
Traverse	170 degrees either side of centerline; rate: 30 degree/s
Rate of fire	16–20 rounds per minute automatic
Muzzle velocity	2,650 ft/s (808 m/s) full service charge; 1,500 ft/s (460 m/s) reduced charge for defilade fire or illumination rounds
Effective range	13 nautical miles (24 km)
Feed system	600 rounds (Ticonderoga class); 680 rounds (Arleigh Burke class); 475–500 rounds (Other classes)

File:USS Cowpens (CG-63) firing 5 inch.jpg

USS Cowpens (CG-63) fires its Mark 45 mod 2

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. It is designed to be used against surface warships, 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-inch/54 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 (114 mm) gun, but it fires a heavier 5" shell, and carries a larger burst charge which 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 barrel (62 calibers 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).