Brain shots with a 22LR have killed many whitetail. 40 yds from an elevated solid position should be easily accomplished. I personally have only used 40gr solids in this role. I was much younger and had not yet learned that a head shot required major foot pounds.
The deer on your private land (like on mine) are probably not harrassed and so are not vigilant. This makes the shot unrushed and controlled. I have never lost a deer to a 22LR because the shots are always appropriate. The deer drops and often other deer close by sniff and paw at their dead companion without startling. Enjoy the venison.
