Val, I'm now of the opinion that Pittu is possibly correct. You have the seating die screwed too far in and its trying to crimp the case neck into the bullet w/nowhere for the case mouth to go. This tries to push the case back but what happens is that the point of the shoulder expands and the case will not enter the rifle chamber enough. loosen the lock ring on the die and screw the die towards the top 1-2 turns,leave loose, unscrew the seating stem several full turns, leave loose. place a factory round in the shell holder, raise the ram to the top and let sit, screw the seating die into the top of the press till it makes contact w/the round. Unscrew the die 1 full turn, set lock ring lightly. Screw the seating stem down till it makes contact w/the bullet. Set its lock ring buy finger pressure only. Seat a bullet in a DUMMY case (1 sized but w/out primer or powder), check for functioning in YOUR rifle. Then you have a base dummy round to put in your die box to always go back to. Now you may commence to make a true dummy round for you rifle w/whatever you want, but don't screw the die into the press much more, do all of your (unless you want to crimp) adjustments w/the seating stem. Good luck-Muddy
