The .45acp Model GKK-45 (Kompakt) is the same pistol as the FÉG Model ACK-45 except for the different model designation for export.
The 'GKK' designation was given to the pistol by the importer, Michael Kassnar of KBI, Inc, after the initials of his daughter. The 2nd K should stand for 'Kompakt', indicating a shorter barrel.

The revolving type firing mechanism, flying firing pin and the rotating safety latch are incorporated into the slide. The barrel latching in the slide is done via three latching ribs. The pistol is equipped with an external hammer with a safety rest to avoid accidental discharge. The revolving type firing mechanism and the external hammer make it possible to fire the first shot directly by pulling the trigger with a round in the chamber, while the gun is unlatched with the released hammer. The hammer may be cocked with the thumb also. The revolving safety mechanism in the slide allows safe loading the latched pistol.