Why two Royal Navy 30 mm gun systems overlap

Does the Royal Navy use both the Oerlikon KCB and Bushmaster II 30 mm gun systems?

Yes. The newer Bushmaster system has reached some ships, while funding delays are blamed for leaving older DS30B systems in service.

The newer Bushmaster installation is intended to replace the DS30B mounting with its Oerlikon KCB cannon. Repeated funding cuts are blamed for slowing that transition. Bushmaster systems have reached some ships, while others are described as leaving refit with the older equipment still fitted. The resulting overlap separates the intended fleetwide replacement from the equipment retained during implementation. An initial claim that the navy might no longer use Bushmaster is corrected during the exchange.