Re: leupold mk4 8.5-25
You start getting a lot of mirage at the higher mags, so even if you have it that doesn't mean it will work well for you all the time. I think you will find the 6.5-20 will do very well for you, even well beyond 800 yds. If you really want higher mag, try looking at Nightforce scopes. They have a scope that goes down to 5.5 and up to 22, which covers a wide range of applications for both hunting and target shooting.