RE: knockdown power... fact or myth?
There is a study they did in that link where they shot several deer with different calibers and noted the reactions. None of the calibers were consistant at dropping game on the spot.
I believe when one talks about knock down power they want something that drops the deer in its tracks. Unfortunately there is no weapon that does that everytime. And a lot of it depends on shot placement. And many actually believe that a rifle can take a deer off from it's feet and litterally knock it down.
Paul