IF your base and rings are on tight, then you have a very bad scope...really that easy. Like mentioned above, for most big=game hunting, a fixed 4X will do for about 99% of all shooting, a big enough field of view for close-in shooting, and enough power for shooting as far a most folks should be shooting. Sadly, they have pretty much fallen from favor, due to much more sexy scopes out there, with big power, etc.
For shooting varmints at ranges from close to very far, then a GOOD high-power comesinto play.
One problem some beginning shooters have, is choosing too much power. They shoot at targets from a bench, with a solid rest, and the higher power really helps with percission aiming, but in the field, with at best a make-shift rest, things are much different.
Bottom line is get a fixed scope, probably 4x is best, or get a good variable, with a power range of say 2-7 or 3-9. For big game, you don't need mil-dots, adjustable objective, etc. KISS.
Mark