5-inch/54-caliber Mark 45 gun

Mark 45 5-inch/54-caliber lightweight gun
Mark 45 5-inch/54-caliber lightweight gun
	5-inch/62-caliber Mark 45 Mod 4, in flat-panel gun turret, test firing on USS Forrest Sherman
Type	Naval gun
Place of origin	United States
Service history
In service	1971–present Mod 0: 1971; Mod 1: 1980; Mod 2: 1988; Mod 4: 2000;
Used by	See Operators
Production history
Designed	1968
Manufacturer	United Defense (now BAE Systems Land & Armaments)
Produced	1971
Specifications (Mod 2)
Mass	21,691 kg (47,820.5 lb)
Length	8.992 m (29 ft 6.0 in)
Barrel length	6.858 m (22 ft 6.0 in); Rifling: 5.82 m (19 ft 1 in) Mod 4: 7.874 m (25 ft 10.0 in);
Shell	127 × 835 mm .R ; Conventional: 31.75 kg (70.0 lb)
Caliber	54 caliber (Mod 1 and Mod 2) 62 caliber (Mod 4)
Elevation	−15° to +65°; Max. elevation rate: 20°/s;
Traverse	±170° from centerline; Max. traversing rate: 30°/s;
Rate of fire	16–20 rounds per minute automatic
Muzzle velocity	2,500 ft/s (760 m/s); 1,500 ft/s (460 m/s) reduced charge for defilade fire or illumination rounds;
Effective firing range	13 nmi (24.1 km) or 20 nmi (37.0 km) (Mod 4)

The 5-inch (127 mm)/54-caliber (Mk 45) lightweight gun is a U.S. naval artillery gun mount consisting of a 5 in (127 mm) L54 Mark 19 gun on the Mark 45 mount. It was designed and built by United Defense, a company later acquired by BAE Systems Land & Armaments, which continued manufacture.

The latest 62-calibre-long version consists 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-person crew (gun captain, panel operator, and four ammunition loaders) below deck to keep the gun continuously supplied with ammunition.