From a ballistics standpoint (the only standpoint I have with any of these calibers...) I believe that Dober is right on this. I just went to Woodleigh's website and they do, indeed, make a 300 gr FMJ in .338. So when factoring in roughly equivalent MV's the .338's higher SD and smaller frontal area should theoretically penetrate better (slightly).
That being said, when I read of all the elephant taken by the old timers with the 7x57 and .303, I can't imagine ANYTHING knowing the difference no matter which cartridge you choose. Scratch your itch!!!
