Probably the 85's core alloy is a little softer, but I sincerely doubt that will keep it from getting through a pronghorn's ribs. I never have shot any big game with the 85, though have killed a lot of varmints (including coyotes) with it, but have killed some big game with the discontinued 60-grain Solid Base from the .220 Swift at 3650 fps, and never recovered one.
Jack O'Connor once wrote about the conviction so many deer hunters had that the .243 Winchester would work better than the .244 Remington, due to the .243's 100-grain bullet versus the .244's 90-grain. He said he doubted a 90-grain bullet in the ribs would do a buck any good.
