I have been working on an auto reset rifle target based on the Larue target, using a 2/3 sized (idpa/uspsa) AR500 target. The cam is working on a pin from the bottom (grade 8 3/8" bolt cut off). There is a spring counter bored into the 1" shaft to keep the cam against the pin by pushing back on the motor. I used double split set collars to allow for adjustment.