I use a 10x44 on my rifle & I have hit 1in targets at 50yds consistently using 16gr Logun Penetrators so I reckon it's just that you get on best with your mag at that setting. Everyone has different preferences so that might be yours. Failing that, it could just be parallax error as previously stated. Also, you might have a few dodgy pellets in that particular tin. Having said that, shooting at them sort of ranges with a 12ftlbs rifle there is a good chance there is going to be incosistencies with the POI as the pellet will have lost alot of its strike energy. I'm probably wrong but it might be worth looking into all the same. I hope that this is of some help.

Regards,

Keith