I have had both, my take is:
Good points, 338 Lapua ;
wind drift, retained energy.
Good points 300 Win mag. ;
Trajectory, burns less powder, cheaper components, less recoil, lighter rifle.
Easier to shoot. Plenty of energy at long range. Normal sized action.
Better component availability and selection.
Bad points 300 Mag.;
more wind drift.
Bad points 338 Lapua;
Component cost and availability. Muzzle blast and recoil. Trajectory. Action compatibility, I.E. you need a larger action. Heavier gun. Harder to spot your shots.
I sold my 338 Lapua to a young man, I couldn't talk him out of it! he wanted the horsepower and thought it was "cool"
600yds no question the 300mag wins, the 338 Lapua advantage doesn't show up until you get further out.
You may want to consider a 7 Mag or 280 A.I. if you are only shooting 600yds?
Hell a 6.5 Creed may be a better solution?
