What am I doing wrong????

[Ken14]

Im having some full length sizing problem with .243 Winchester cases. About half of the cases will not allow the bolt to close, I have used two different die sets, I lubricate with Imperial die wax. Anyone have any answers? I load for numerous other calibers and do not have trouble with any. I have even used two different rifles..Both Remington 700's. Both rifles cycle factory ammo fine.

Thanks for all input.