Originally Posted by Simo
Nikko Stirling 10-50x60 Diamond
Ok, that changes things.
Forget what I said about turning the objective lens, it's a sidewheel on that scope, and I'm assuming he is turning it for the correct range (and not just the top turret).
If he's adjusting focus for 15 and 45 then it isn't likely to be parallax error.
Also check its not something daft like he originally zeroed the rifle when it was windy.