For longer ranges on animals as heavy as northern whitetails and mulies I would stay away from ballistic tip style bullets and use more of a controlled expansion bullet. My choice for the 270 wsm in your application would be a Barnes 130gr XLC.
I really like ballistic tip bullets for lighter game, I have had goodaccuracy and performance with the 270 wby mag on pronghorns with the 130 grain nosler BT at 3290 fps. (1/2" groups @100 yds.)