I would go with the .243 as a minimum for deer.Yes,I know thousands of deer have fallen to the various .22's,but they are rather light to ensure clean kills.Why not look at a .25-06 or 7mm-08?? Loaded light,good for varmints...loaded heavy,great for deer.Your best shot with any caliber is still a broadside heart/lung shot.Shooting at an animals head is risky buisness,as there is no margin for error.A shot to low or forward will result in a horrible wound to the jaw and nasal passages.Stick with a broadside and just aim behind the shoulder to avoid the bone.