I forget all of the technical stuff about why this happens but, when you sight your scope in you should sight it in on the highest power.

If you were to sight it in on the lowest power and then crank it to the highest power, if it does have any movement in the point of impact, it is magnafied this way. There will be less movement in the point of impact if it is sighted in on the highest power.

It is not suppose to move any either way but if there is any movement sighting it in this way will minimise it.