Jim,
That's still a pretty big buck! I've only killed four mule deer as large or larger, and doubt if we've killed any Montana whitetails that large. I would definitely vote for the 100-grain.
Another good big-deer bullets in the .257 AI (or indeed any .25 caliber cartridge except 1-14 twist .250 Savages) is the 115 Nosler Partition. Have only recovered one, and it was from my biggest whitetail. He was 88 paces away, quartering toward me, and I put the bullet high on his shoulder, because his lower body was hidden by a deadfall. It took out his shoulder and spine do I didn't need a blood trail. Found the bullet under the hide at the rear of the ribcage on the opposite side. The cartridge was the .257 AI.
