It can be parallax except those like Blaine and myself shoot up to 10K rounds a year and know how to take that out... Its not in our case, related to the scope...
Its simply the bullet not going totally to sleep. Very common with high BC bullets.
It has nothing to do with target size either, my targets are made for whatever I'm shooting, IE 300 is different than my 600 yard targets, I actually make them each time I shoot after I see what power of the scope I can see best with that day due to mirage issues unless I'm shooting at night.
Of course if you shoot diamonds, target size isn't as critical.
