Overall for pronghorn I think just about any jacketed bullet weighing at least 65 grains with enough velocity behind it will work well. I know this is going to shake up the kettle real bad, but I just can't see using super premium bonded bullets on game like pronghorn. Spend that money on accuracy instead. Just my experience though.
That's been pretty much my experience also. I've killed somewhere around three dozen pronghorns, all with standard cup and core bullets. I've always felt that bullet placement (accuracy) is more important than bullet construction...as long as you're using a bullet that is designed for the size animal you are hunting.
There's been a lot said and written about the cost of premium bullets vs standard cup and core bullets. As a handloader, premium bullets are about twice the price of cup and core bullets. So for my .300 Weatherby, it would cost me about $0.27 per cartridge more to load 168 gr TSX bullets than to load 165 gr Ballistic Tip or GameKing bullets. For my .257 Ackley, my favorite pronghorn rifle, it would cost me about $0.36 per cartridge more to load 115 gr TSX bullets than to load 115 gr Ballistic Tip or 117 gr GameKing bullets.
At todays fuel prices, one gallon of diesel for my pickup costs more than the cost difference of half a box of shells loaded with premium bullets rather than standard cup and core bullets.