Wooow, specifics? Ammo, gun, rifling twist........

I have a friend that has a 1-8" twist in his 223. His groups were not good at 100 yards (3-4") if I remember right. When he gets to 200 yards and beyond, they tighten up.

Also, the faster twist is for shooting heavier bullets. So, possibly if you have a fast twist with a light bullet, or a slow twist with a heavy bullet, this could be your problem.