The 5-inch/54-calibre (Mk 45) lightweight gun is a modern naval artillery gun mount consisting of a 5-inch (127mm) L54 Mark 19 gun on the Mark 45 mount. It is designed to be used for naval gunfire support and against surface targets.

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.

An advanced version, the Mk 45 mod 4 lightweight gun, uses a longer barrel (62 calibre in length versus 54) for more complete propellant combustion, higher velocity and greater utility as a land attack weapon.

Function Naval artillery gun
Manufacturer BAE Systems Land and Armaments, Armament Systems Division
Designed 1968
Weight 21.7 tons (mounting weight)
Rate of fire 16-20 rounds per minute (automatic)
Calibre 127 millimetre (5 inches)
Length 9 metres
Barrel length 6.86 metres
Barrel life 8,000 rounds
Range 24 kilometres
  • Destroyer, Guided Missile (DDG)
  • Frigate, Helicopter (FFH)


Naval artillery gun