Joe,

This does happen to some without any defect on the rifle, scope or ammunition. Alot of times changing from lower power to higher power your crosshairs are smaller on the target giving a better point of aim. This being said the most it should be off would be 1/4" to 1/2" max if your shooting well. When sighting in a scope for maximum preformance one should always sight it in on high magnification for best groups. Once you turn down the scope you won't notice any change on groups at all.