Gentlemen, the previous poster stated he killed a 2200 lb domestic bull with a 22 SHORT between the eyes.............to which I called BS !!!
Don't want to get too old of a bull then, something in the 6 month 300 lb range sounds about right!!! 22 short still won't kill it!!
Ok... I'll start with a response to the OP's question... your 150 grain load outta a .308 will take any blackie that ever walked the earth (regardless of size) as long as YOU do your part and put the pill through the lungs.
Now for the quotes... Doug, I agree about a bullet "between the eyes" not getting it done, but not that an LR round won't get it done... here is a story;
My dad and I were butchering a large Highland bull one November (which we normally do with a Mini-Mag solid outta one of many rifles)... but on this day, my dad grabbed his .38 S&W... and loaded FIVE bullets... I asked him what he was going to do with FIVE rounds??? He answered "well you never know" (perhaps he had a premonition)... at any rate (I should not admit this on CGN, but....) I have hunted, pretty much every game animal available in Ontario (and many others around NA), for 40+ years, hundreds of big game animals and many thousands of small game and waterfowl... but I have a hard time walking up to a domestic animal and popping it at point blank range (go figure)... our usual routine is that I stay in the house until I hear the shot, give it a couple minutes and then go and take care of the bulk of the butchering... On this occasion, I heard the shot, and then 30 seconds later another (I figured it was just insurance)... but 30 seconds later a third shot, then a fourth, then a fifth... what the heck!!! I ran around the corner expecting to see the bull standing over my father on the ground, but heard him yell out... "get me more bullets!" I ran back into the house and grabbed a handfull of bullets and back outside... there was the bull standing spraddle legged, still on the hoof... we quickly loaded another round and put it in his head and down he went... without a twitch... to satisfy our curiosity we skinned out the skull... the first five rounds formed a circle stating between the eyes and around the perimeter of the brain, maybe a 5" diameter circle... the last shot was right in the center of the circle...
I say that to say this... that even at 3 feet caliber and bullet take a backseat to placement... All of the Mini-Mag'd steers went down cleanly without a hitch (but as you point out these are not .22 Shorts... and the "right" spot is NOT between the eyes!)