The shoulder bone would be my biggest concern. Pronghorns have bones considerably harder and tougher than many animals. In fact my recollection from some old research is their bones are almost 10 times as tough as cow bones. I have seen pronghorn shoulders do some odd things to bullets over the years.
If you put an 85 in the ribs, however, it will kill even the biggest buck neatly, and while it will drift a little more in the wind than a 100 or 115 Ballistic Tip, the difference doesn't show up until beyond 300 yards. And even at 500 the 85 at 3250 will only drift about 4" more in a 10-mph crosswind than a 115 at 2900.
