I've never shot, or even seen for that matter, a black tail deer but I think you have an excellent idea. That would have to be a dandy piece.
I had a .243 rebarrelled to a .260 this year and shot a couple of white tails with it. I was shooting 140gr Rem Core Lokt bullets @2600fps (I never Chronied the load) and it did a number on the ones I shot.
If I were to leave tomorrow on a mulie hunt, I think I'd leave my tried and trusted 7-08 at home and take a .260