Even a .22 CB could kill you if it hits you in the right place. Hell, even tripping over badly and hitting a rock has killed people. having a wider or deeper wound channel increases the amount of the body that is hit, and therefore statistically increases the odds that something important will be caught in the volume that is hit and subjected to the kind of trauma (with an A not an E) that breaks it. Rifle shots are only more effective because they have more energy to break more stuff, hopefully vital stuff, by penetrating more, expanding more, and causing more to stretch to the point of breaking so hopefully something important will be broken.