I knew a guy for a while that hunted a private ranch for our Blacktails. He and his buddy used a .22 Rimfire Magnum with standard 40 gr. HP's.
They shot nothing over 125 yds. out and nothing less than 3 pointer's which usually are 4 yr. old bucks.
All of them were killed with neck shots. All went right down, etc.
Be careful doing this. If the bullet hits high, the buck will go right doiwn. Then he will recover and run off. They seldom bleed much even from much more powerful rounds. E