The JBM calculator is fun to play with.
You can enter various conditions and see the predicted drop at 600.
Plug in your best guess for range conditions just to start.
Elevation, Pressure and Temperature will get you close.
A 4DOF (or 6) calculator uses more earth variables but nothing beats fine tuned DOPE from real shots.
A Mil/Mil FFP scope takes a little getting used to when shooting on a target that's based on MOA.
You've had recommendations from 3 to 3.5 mils. Split the difference 3.2/3.3, and that's UP on the turret

The 9 ring is 2 MOA across. Anything from 6" high/low/right/left will at least be a "9".
With a 0.1 mil/click scope that's +/- 3 clicks from the edge of a "9" to the center.
While an "X" cold bore would be great, a "9" would be acceptable. After a few sighters you could fine tune your dope.
Windage will be your biggest challenge (it's still mine).
Wife and I leave the house in about an hour for a 600yd match.
Flat land down south, using Mil/Mil FFP scopes. I seldom see more than +/- 0.1 Mil variance in elevation for range conditions, maybe +/- 0.2 Mil Summer to Winter.
and again, good luck and have fun.
What does 3 clicks do @ 600 yds with a Mil scope?
At a practice session the wife needed to come up a little, about half an MOA, and went
3 CLICKS on a Mil scope.
