I have a question on bullet weight. I always hear people (well, read I guess) saying you should use a heavier bullet when hunting bigger animals. Or say something like "you need at least 100gr for a red deer" or "don't shoot a buffalo with less than 350gr". By the way these are examples I'm not interested in whether they're true or not. I have an engineering background so should be able to work this out from a mathematical point of view but why is this?
I understand about momement, (mv) and energy (1/2mv^2). But for these, velocity is at least as important as bullet mass. So that can't be it.
I understand about penetration and sectional density. The more 'pressure' the bullet imparts the more it will penetrate for a given shape and velocity. But SD is not the same as weight - only in the same calibre. I 160gr 6.5mm bullet should penetrate better than a 160 gr 30 cal bullet at the same speed. So that can't it.
So what is it - is there some killing component I don't know about? Surely a 95gr 243 will kill at least as well as a 100gr 308?