I suspect your problem is to much crimp. The only reason it could be neck tension is you have a faulty sizing die (not likely).
With my RCBS dies, I seat and crimp in separate steps. Don't see why you couldn't do this with the Lee die you have. Back the die body out far enough than it will not be applying any crimp. Set the seating stem and seat the bullets. When bullets are seated, back off or remove the seating stem and adjust the body downward until you crimp enough to remove the case mouth expansion. Over crimping will crush the case and cause the loose fit with the bullet.
A lack of planning on your part does not necessarily constitute an emergency on my part.
Last edited by serf 'rett; February 13, 2013 at 12:38 PM.