Here is the quote for the Vortex Viper 6.5-20x44mm and the 6.5-20x50mm: Mil-Dot Reticle allows the user to do range estimations as well as estimating holdover, wind drift and lead moving targets. It is very important to understand that in order to use these features, the scope must be set at 14x magnification. Of course, the standard center crosshair can always be used at any magnification.
These scopes are SFP and not FFP scopes. Sorry to tell you may have ordered the wrong type of scope if you wanted a FFP scope so you can range at ANY magnification you are set at.
I had to cross the Viper and Leupold off my list because they are SFP scopes.
Looks like I may get one of these: Falcon Menace Optics
or the new Weaver Tacticle FFP scopes: Weaver Mounts - Tactical
I called Weaver and they told me that they are in the inspection stage and not selling them yet. They told me that this scope IS a FFP.