Have you thought of using a LBT style bullet. A few years back a friend of mine killed a Mule Deer Buck with a Cast Preformance .45 cal. 300 gr. LFNGC on top of 100. grs. Pyrodex Pellets. He hit the buck in the front chest @ 200 yd. dropping him on the spot. The bullet was found between his butt and hide. Good luck.