Re: I\'m not stumped
Sometimes the case when being sized puts enough added pressure on the die it just keeps the die from coming down as far as it did with just a shellholder against it, as you've found. You'll now find that the smallest increment (read 1/64 to 1/32 of a turn) of adjustment will alter headspace considerably. You should go back to where it was and make very small adjustments until a case just chambers, note the reading to the shoulder and do a few more to verify it is consistant, then possibly set them back just .001, but probably .002 more from this if bolt lift is heavy when you fire them the next time, or do it now to insure they will not be. You will not need to set them back any more than .002 from where the bolt just closes with some felt resistance though. I would set them back in steps of .001 to insure you have not went to far and you know exactly where they are too tight, then you will know by measuring the cases next time if it is indeed tight headspace. Good luck.
After each sizing the cases will work harden more and more depending on the amount of working the brass undergoes each time so you my want to monitor the length to the shoulder on a few each time you size to see if and when you may need to slightly adjust the die to compensate for a change in headspace due to a change in the brass's springback quality gradually being altered.