RE: Sighting in at 300 yards ??
He said he got pretty good groups at 200 yards, he didn't say they were right on. You can have a good group way over on the edge. I have seen a lot of long range shooter in action and they usually have wind flags every 50 yards. The wind at 500 yards can sometimes be blowinjg from a completely different direction. I don't think that in this case is was all the wind. 300 yards is a long ways. Ever notice how small a target that a deer is at that range?
Targets at 500 are fun to shoot at. If you miss you can laugh and try it again.