The Autococker Trilogy was released in 2004. It was an attempt by Worr Game Products (WGP) now owned by K2 to produce a cheaper entry level Autococker. In this simplified new design the front block & 4 way valve was integrated into the main body which made upgrading the marker more difficult.
Autocockers use low pressure air supplied by a regulator to power a small ram to re-cock the marker on firing. A 4-way valve connected to the trigger mechanism switches the air from one side of the ram to the other to achieve this. Pulling the trigger opens the bolt whilst releasing it closes it. For this to work properly, the whole system needs to be timed so that the marker fires just before the bolt is opened. Whilst most Autocockers are mechanical. Some later models had electronicly controlled 4-way valves and sears which allowed for a higher rate of fire.