Welcome to the Dark Side of the Moon. I shoot a Vari-X III 6.5*20 with a mildot on my varmit rifle in .243. With Mills, you can compute your holdover as per your BC and velocity then just have your little chart which I tape to the stock and to the bottom of my range finder. Works for me. As for the varmit reticle, those graduated lines have specific minutes of angle so you can figure out the drop with your loads. line one below the crosshairs may not be 300 meters and line two may not be 400. Might be 250 and 375 for example with those kind of hyper velocities. But, it ought to work just fine.
Either way, for P-Dogs, having a spotter is required b/c he can call your shots and then you can just vary your holdover for elevation and wind to account for your misjudgment and then you can fire for effect once you are laid in.
Some days, when we are just on a killing spree, it might take two, three or four rounds to get the first hit on a particular hill with several dogs out where we shoot b/c of the wind and ranges pushing between 300 and 500 yards, but then you can get all the other dogs usually on that hill with single shots. We don't really bother doing any ranging or calculations. Might fire 300 rounds.
Other days, we take our 300 mag senderos and calculate every shot with a rangefinder and the wind meter, then we try for one shot kills. Might fire 40 rounds only.
Depends on you mood and the purpose of that trip.
