Both would work, but personally, I would choose a 2X. A 2X is easier to hit with at close range targets do to its larger field of view, and less magnified "shake". At longer ranges, you will be using a rest, probably on game that is not spooked and moving, giving you time to place your shots with a 2X about as precisely as you could with a 4X. If you can afford it, a variable would be a good choice for a handgun with the .308's performance range.
Larry