Is this strictly competition, tactical, target, or hunting? Or some combination thereof?
For the max range and caliber quoted:
Hunting: someone else can chime in
Target: As high of a power as you want, but keep in mind with extremely high powers, such as 40x, even your heartbeat can make the POA jump.
Tactical: 10-15x. Could go as high as 22x, but I would not recommend. 15x works well for me out to 1,100, a good balance of magnification and ability to acquire targets without searching or having to dial back. Variably power is nice, but not necessary. For most people, myself included, the variable power adjustment almost never moves. Therefore a FFP is basically pointless as well. For what you are wanting to do, a fixed 10x would be plenty sufficient.
Competition: depends on the type of competition. If it is F-class; same answer as for target. If you are talking about tactical comps, dialing in and out under time and pressure, mil-ranging, rapid target acquisition; same answer as the tactical.
The only thing a magnified optic, or a relatively higher magnification, actually does is give you a more finite point of aim. It does not make the weapon or the shooter more accurate.
Also, consider what direction you want to take this. A barrel can be trued or changed out, a receiver can be trued, a stalk can be bedded or changed out, but once you've bought glass, that's it, until you can afford new.
Make sure you get one with adjustable parallax for the ranges you are talking about (not to be confused with focus) Get dials that match your reticle, and badger ordinance rings and base. Align, lap, level, torque, loctite, plum test, box test, bore-sight.
Brands:
Nightforce (my personal favorite)
US Optics
Schmidt and Bender
Swarvoski (spelling)
As a general rule, your glass should cost twice as much as your stick. Buy once, cry once.
