I haven't noticed much parallax change. I have noticed POI change with temperature. When I bring the gun out of the AC in the house it will be off 3 or 4 clicks high and right at 30 yds. as the gun warms up it returns to where it belongs. If you leave it out in the sun it goes 3 or 4 the other way. When at a match I keep the scope covered with a towel, this helps a lot. My HW100 tends to move a little more then my Steyr. Tom