I was recently playing with the 308 at 1800 yards (215 Berger, 2600 fps). I was able to dial a dead on hold (22.8 mils) with 10 mils remaining in the erector, plus 10 mils on the reticle.
I'd guess you will have no problems with the flatter 300WinMag. 20 moa base will probably be fine, but it leaves a lot of 'down' in the erector.
Shane
