MK-45 Mod-4 Naval Gun System live firing

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.[1] It was designed and built by United Defense, a company later acquired by BAE Systems Land & Armaments, which continued manufacture. The later 62-calibre-long 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 which can be fired under full automatic control, taking a little over a minute 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.