25WSM was referring to bullet stability, not wind affects. If it is wind (unlikely), then the groups will have an extreme horizontal dispersion, but vertical should be relatively small.
As mentioned, check your targets and confirm that none of the bullets are hitting at an angle. What twist rate is the rifle, and what weight are the factory Nosler BT? If you have marginal stability, the bullets could be getting severely disrupted between 100 and 200 yds, though I'd expect them to shoot worse than "ragged hole" at 100 yds if you're seeing 8" at 200.
Is this from one session of shooting? Did you fire a few groups at 100, then switched to 200 yds and got the extreme spread? Or is this an observation based on going back and forth between the two ranges? If it's the former, then it's possible something came loose (scope, action screws, etc) between 100 and 200.