My questions involves the field adjustable turrets with MOA marking. Loking to buy a scope with this otion and trying to decide whitch one. And not sure how they work at far as starting from the sight in range. 1. After sighting in for say 100 yard zero, how do you get the turret to zero? Do you take the turret off and then reinstall wihere it sits at zero? For example lets say from the factory i am at 3.75 moa for a 100 yard zero. Is it possible to to somehow get the turret to 0 moa without moving the cross hairs? So that then If I need to go up 6.5 moa for 400 yards I would just move the turret to 6.5 instead of adding 6.5 to 3.75 for 10.25 MOA. 2. The 3 scopes I am looking at is the Leupold VX-II, Nikon Monarch, and Vortex Viper. How do they compare as far as zero stops go. Is one better than the other? Thanks!