Of course I'm biased
(selling a 300 wmag) but I found the 300winmag to be easier to shoot at 1000m. The only reason I can find is that firing a heavier bullet you're less punished by the wind.
Same day, same conditions, my group in 308 was more than double than the 300 Wmag one.
Same day, same conditions, my group in 308 was more than double than the 300 Wmag one.