When using our full length sizing dies for rifle cartridges, the die should be turned in to touch the shell holder and then 1/4 to 1/3 turn more so that there is no daylight between the top of the shell holder and the bottom of the die during the sizing process. This is the preferred method because the act of sizing sometimes results in flex that prevents the shell holder from touching the bottom of the die.
Lee dies are designed so that the shoulder of the case is not sized until the very top of the die has been reached. This is done for two reasons; first, we do not want the die to overwork your brass and second and more importantly, we do not want to invite headspace problems. Pushing the shoulder back too soon can create a situation that can eventually cause case separation and a dangerous situation.
If you notice that your Lee Die does not appear to push the shoulder of your case back, ensure that you are adjusting the die so that there is no daylight between the top of the shell holder and the bottom of the die during the sizing process. If you see daylight at the top of the stroke, readjust the die downward and repeat sizing until it disappears. If your case is still difficult to chamber, you can send the die back to us with a sized case and we can modify the die to minimum SAAMI specifications.
Lee Precision, Inc.
4275 Highway U
Hartford, WI 53027
https://leeprecision.com/files/instruct/returnform.pdf
