You"ll need alot more than a big scope to shoot 700-900 yards with a .308.
About the only thing that the .308 will have enough energy left to kill at that range will be Squirrels and Chipmunks.
You aint planning on shooting Alvin are you ?
I would have to respectively disagree on this one. Having used a .308 for over 20 years now on game a lot harder to hit at longer distances than bear or deer… I can say (from experience) that a .308 does carry enough velocity and energy to kill almost anything you shoot at out to about 7-750yds… IF you make a GOOD shot. The trick is to understand the angle that the bullet will be traveling at that distance… But, as has been said on here MANY… MANY times before, if you HAVE to take a shot over 3-400yds… you aren’t hunting… you are target shooting. As far as scopes go… get whatever you want to get… just keep it on a lower power when you are hunting and you’ll be just fine. I prefer a fixed 10X with a mil-dot recital and an adjustable objective. KNOW your equipment and KNOW your hunting area and you’ll be just fine.