You have to remember the case spings back when being sized or fired. What you really need is a headspace gage period.Then while sizing you should have the hornady tool to measure how much you are setting the shoulder back during resizing.If the sizer is screwed down till it touches the shell holder you dont really know what you have until you measure it first to see how much you are bumping it back. What I do is back off the full length die one turn and size one,measure with the hornady tool,screw in a 16th of a turn till you get .002 thou set back and stop. Try a dummy case in the chamber and close the bolt.If it closes easy you are there.You probably have a headspace problem.The gages are about 30.00,and it is absolute insurance to get it right.Remember to remove the extractor before checking the headspce or grind a relief to clear the extractor.