Rheinmetall Oerlikon Millennium Gun
The Rheinmetall Oerlikon Millennium Gun or Rheinmetall GDM-008 is a close-in weapon system designed by Rheinmetall Air Defence AG (formerly known as Oerlikon Contraves) for mounting on ships. It is based on the 35/1000 revolver gun land-based air defense system and uses Advanced Hit Efficiency And Destruction (AHEAD) ammunition.
Source: Wikipedia — Rheinmetall Oerlikon Millennium Gun (CC BY-SA 4.0)