Information Source: Lee Precision


Neck Sizing with Full Length Dies

We do not recommend neck sizing with the full length sizing die because the head space dimension of the case may be adversely affected.  When you back the full length sizing die out from contact with the shell holder, the die will still reduce the body diameter of the case, which in turn causes the base to shoulder dimension to increase.  This can make it difficult or impossible to close the bolt, because of insufficient headspace.