It's not supposed to fire when it gets to the bottom. Is it airsoft or IR? I'll bet that when the gun reaches the bottom of its travel it's touching something or pulling a wire or something similar and tripping the gunfire. If it's airsoft, does it fire a BB at the bottom or just give sound & recoil? If there's no BB coming out I'd look at the recoil trigger at the back of the airsoft unit, to see if it's triggering at the bottom of elevation travel. As for controlling up and down, if you look at the mechanism it seems to me that the only way to do that would be to obtain control of the polarity going to the motor (you'd have to be able to reverse the direction of the motor). That's a little beyond me right now, but it's something I'd like to learn about. I'd also like to make the speed at which the turret turns proportional. Maybe someday. :-)