When adjusting the windage or elevation have the posi-loc backed out a couple of turns. Once the zero is set you turn the posi-loc in until it makes contact (you can feel resistance). Don't turn it in too tight. You are mechanically locking the agistments. After you tighten the posi-loc check your zero. Since you have removed any backlash out of the adjustments the zero usually changes some. You have to just zero it and try it until you get your scope zeroed. I have it on one scope and I like it. It can be a bit of a pain to get zeroed the first time. Dave