Kutter and the others have given good advice, but you might also try running the cases through the seating die, then the sizing die. To save the rims, you should remove the expander button and seating plug from the dies and knock the cases out with a dowel or punch while putting pressure on them with the press handle; if they wont move with a reasonable amount of pressure on the handle. It helps to know where the resistance is coming from. If you smoke a case, or color it with a felt tip pen and run it into the die, the problem area will be where the color is rubbed off the most( may be more than one area). If it is in the shoulder area, annealing the area as described above, but guard against making it too soft or you may collapse the cases. If the problem is the solid head area, you might have to make( or have someone make) a ring die of small enough diameter to size the head, and push the cases in with a hydraulic press or vise ( size the flash hole and "uniform" the primer pocket afterwards). If the solid head is only a small amount too large an alternative is to turn or polish a small amount off.
Mike
