Would a .40 cal pistol be sufficient to cleanly kill a deer with?
Kill a deer? Sure.
Good enough for hunting them? Nope.
My thoughts prezactly.
In the last 14yrs I've shot well over 100 deer and elk with a .40S&W from a Glock 22. They've all been easier, closer shots than you'd encounter while hunting because they were crippled by motor vehicles first. Long story short, the performance is not inspiring with anything other than head shots. Given half a chance I use a long gun instead.