The Mk-45 (5-inch/54-caliber) lightweight gun is a modern U.S. naval artillery gun mount. It 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 three-man crew (gun captain, panel operator, and ammunition loader) below deck to keep the gun continuously supplied with ammunition.