The 5-Inch/54-caliber (Mk 45) lightweight gun is a modern U.S. naval artillery gun mount consisting of a 5-inch (130-millimetre) L54 Mark 19 gun on the Mark 45 mount. Originally designed and built by United Defense, it is now manufactured by BAE Systems Land & Armaments after the former was acquired. The latest 5-inch/62-caliber 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-man crew (gun captain, panel operator, and four ammunition loaders) below deck to keep the gun continuously supplied with ammunition.