Cal, what I do know is that I can get 200fps more out of a 2" shorter barrel when comparing the 270 and 270WSM. So, add in the shorter action and less barrel and you have a shorter, lighter gun. I haven't compared the magnums but from all the reading I've done, it seems a 300WSM can match a 300WM and the same for the 7mm with a 2" shorter barrel. No big surprise there as the fatter case should be a bit more effcient and truthfully, the loss of velocity per inch of barrel in all cartridges isn't that significant. It's not hard to believe that the WSM can make up 50fps...at least for me.