Let me throw this idea into the mix. No matter of just how good your scope is you are not going to walk up to the 600 yard line and hit the in the center target right away. You need some sort of spotting scope to read wind conditions to even come close. The spotting scope will cost you about as much as a quality rifle scope. And then there is the scope stand to buy.
Once you start shooting at 600 the guy who tells you he shot his last buck at 600 yards you will know he is full of it. It takes a lot of work to hit the center of the target at 600. And the more you go out the harder it gets.
God Bless our Troops especially our Snipers.