My theory issmaller faster bullets leave lots of damage but deer usually dont know what hit them for a few seconds. It seems deer feel the pain of slower moving bullets and drop more times than not.
of course this is just a theory.
This is a theory that I certainly don't share after having personally killed about 50 deer and seeing many others killed.The simple fact is that the more damage that is done,the faster the animal dies.My experiences have shown that the high velocity cartridges using rapid expanding bullets cause the largest wound channels and therefore the most rapid deaths.The biggest reason that deer run after being shot with a cartridge such as the 7mmremmag is that either the shot placement is not correct or because they use a heavy bullet such as a 175gr that is moving slower and expands less rapidly,therefore doing less damage.