USS Cassin Young DD-793 - MK 51 Gun Director


Each 40mm Mount has a corresponding Mark 51 Gun director above them.


The Mk 51 range keeper is used  to aim the 40mm AA gun more accurately. It did this via a gun sight coupled to an air driven gyroscope that would determine the lead and lag of aiming by how fast you were turning the gun director in order to track your target.

The 40mm guns had two 440 volt AC current motors on it to rotate the gun platform and to raise and lower the gun barrels as needed to aim the gun. Add a firing trigger to the right hand handle bar. When the operator has the target in the cross hairs he pulls the firing trigger. If the gun captain standing on the 40mm gun has his firing trigger pulled the 40mm gun mount will commence firing and will continue to do so until one of the triggers are released.


If something were to happen to the Mk51 the gun would be aimed and fired via the crew on the gun mount and not remotely from the Mk51 gun director. However this would not be as accurate.