Heh, those are not there for magnification. Those are there for adjustment for wind (side-to-side) and elevation (up-and-down) so that a sniper can zero in on the target in their scope. These are precision adjustments and you need to be in a set position and calculate the two things I just mentioned to use them properly.
EDIT: There are scopes that do magnify, I'm not saying they don't exist. Usually though it's a ring on the towards the rear of the scope, just in front of the eyepiece. These types of scopes are not typically found on sniper scopes. More of a hunting application than anything. Pretty much like using binoculars. (there typically would also be a second ring, towards the front maybe? not sure, but it's for focus after you get your zoom.)
Those scopes would be a lot more practical, but they're also for smaller magnification. Though for a game, I can see a 5x/10x coming in handy and would be a lot more practical and realistic than a variable zoom.
No knobs to switch between them, right?