I was at the range with my savage .223 with a burris tach 6.5-20x50. I had it zeroed at 100 yd at 20x and the parralax set at 150. I then zoomed out to 10 x sense thats what i usualy shoot at. I the decided to move the parralax at 100 instead of 150 sense i was shootin at 100. It then started hitting 1-2 in hight and to the right. Can zooming and adjusting parralax effect the zero like that. Thanks for the input.