I agree with James, the .308 covers most of the same ground as your .257 Roberts and your .270. Not that there is anything wrong with the .308 Winchester, it just seems a bit redundant to your current rifles. Now the .300WSM would cover bigger critters at longer ranges more effectively than what you currently have, although some would argue for an even bigger case/bullet to really provide a step up in game class. One other question would be as to whether or not you handload? If you do, then I see no problem with the .300WSM, as you could load it down and ammo cost is not really an issue. If you don't handload, then be sure to take into account the higher ammo prices on the Short Magnums and their somewhat limited availability. I would hate to have to buy factory ammo for my .270WSM.