The gun was first deployed in 1971 as the Mk 45 Mod 0, and has been updated in the more than five decades since.

The company will extend the barrel of the Mk 45, strengthen the gun mounts and incorporate a fully digital control system.

The US Navy has contracted BAE Systems to upgrade Mk 45 5-inch naval gun systems, including the overhaul of existing systems, to the Mk 45 Mod 4 configuration. This modification, worth $23.5m, supplements a prior $47m contract,