Bulldog,

If you use 500 Grain's reduced load for your dad to become familiar with the gun then use full loads for the hunt you will have the best of both worlds. He'll only need to fire a handfull of full loads loads here to make sure his grip on the rifle is adequate and confirm his sight picture. Perceived recoil when you're shooting at live game is nothing compared to perceived recoil at the range. I'll add that perceived recoil when you're standing at the range is a whole lot more tolerable than perceived recoil at the bench.

JPK