velocity and resistance is what expands bullets, it also causes what we call bloodshot meat. the higher the impact velocity the faster a bullet expands. the farther a bullet travels before impact the more it slows down, this is why I refrain from heavy bone shots at close range.
deer are considered light thin skinned medium game, the premium controlled expansion bullets expand slower than cup core bullets, in they're designed window on velocity they expand just like cup/core bullets, just they perform in a higher velocity window.
cup/core bullets work best from 2500-2800 fps, premiums do the same at 3100-3300 fps, at slower velocities they expand less, basicly your looking for a happy medium on deer sized game, to find a "happier" medium with mid level cartridges, just stay off the shoulder till the bullet slows a bit, in the smaller cartridges you can get by with solid hits closer.
RR