Don't be disheartened, look at the vertical spread, it is still sub-MOA at 200.
A 5-7 mph bursting wind from left to right explains the horizontal spread. Shooting from a lead sled means that your technique was as good as it could be, except that you had a hard time accounting for conditions.
No worries mate, shooting in the wind is more art than science some days. Last time I shot at 500 yards the flag at the firing line was standing straight to the left, the 300 yard flag was straight to the right, and the flag at the target line was dead calm.
Machine guns are awesome until you have to carry one.