My manuals don't show any real difference between the 7MM Rem mag and the 7MM WSM until you get to the heavier bullets. With heavier bullets the WSM can't keep up with the older REM Mag. Some of my manuals don't even list the WSM with heavier bullets. Deep seating of the bullets with the WSM limits its powder capacity. For this reason I don't see the 7MM WSM ever comming close to the popularity of the Rem Mag or its 270 and 300 WSM's. It may however hang on.