Not enough of one to be a problem. If you are going to be using .38 spl. for practice use the same point of aim you use with your S.D. loads. As long as the group is together and on the center line of your target. Your group being a bit off the mag. loads point of impact is not really a big deal. But do practice enough with the magnum loads to be comfortable with the recoil and know where your point of aim needs to be.