Are you using brass that was first fired though your gun? If not, you may need to adjust the die down to set the shoulder back a little. You may have a tightly chambered barrel. Get a good max case gauge or pull out you barrel and use it for a gauge. The case should drop in with out help leaving the base even with the chamber hood (the little protrusion on the top of the barrel).
If a resized case does not drop in easily you need to adjust the die 1/4 turn increments until you get the proper shoulder orientation.