I would also like to thank you for your service and wish a safe return!
If 400-500 yards is your max and the game is deer, I'd stick with a standard .270, 7mm or 30-06. (Probably going to get hit hard for this one, but I've never really been a .308 fan, there I said it, let the slaughter commence
) Plenty of power out to that range, easier on barrels than the mags, easy to find components, cheaper brass and easy recoil. There's no reason that you couldn't use any of these calibers for your medium varmint gun either. To the contrary, it's great to practice hitting those small targets with your hunting rifle. Could keep costs down too.
I love my Savage rifles and do not hesitate to recommend them.
It sounds like you're just getting into the long range side of things and should you decide to bump up to a larger caliber, the Savage is only a bolthead and screw on barrel away from anything you want to upgrade to.