I am mauling over a custom rifle and after much research I have a question that I can not find the answer for. Can any one tell me if any real terminal ballistics are gained from going from lets say a .308 to a 300 WM? Both shoot the same diameter bullets but he 300 WM does it a little quicker and of course can loft slightly heavier bullets; but still they are the same diameter. If one was going to step up to a magnum caliber to gain terminal ballistics wouldn't one be better suited to chose a larger diameter bullet like a .338? What should person be looking at when trying to decide on a caliber...sectional density, energy, ect?