Actually, with everything else being equal, the 300 Win Mag will have at least 100 feet per second over the 300 WSM. It would be impossible for the WSM to outperform the standard 300 Win Mag, as the case is smaller and holds less powder. In reality, there is virtually no difference between the two cartridges ballistically, not enough that a deer, elk, or the guy behind the gun is going to see any difference whatsoever.