The only "blood trails" (if you can call it that) we've gotten from 22 and 24 CFs have come from fine pink mist. Can't see it unless on snow. Even then my old eyes don't spot it well. My son has done so.
Just an impression: reliable blood trails start at around .308". Not saying 25s to 7s are no good. They are great killers, as are the 22s and 24s. But in thick cover (as here) a deer cartridge starts with a 3......or 7.62.
Mathman's point is valid. And mostly explains why arrows and large bore low-velocity rounds leave better blood trails than .300 Wins. It's a matter of time under pressure. At zero blood pressure there's not much leaking. Not much running, either. Not just external bleeding, also correlates with extravasated blood in tissues ("bloodshot").
Shot a few deer with sub/transonic .308" 170s. Blood trail was not great, but decidedly better than with full-speed 22s and 24s. Less mist. Longer avg runs. Low in the chest, more bleeding, high in the chest, less.
