Cases will lengthen as they are being FL sized until the case shoulder comes in contact with the die. The RCBS Precision Mic is a useful tool when setting up your dies. I have not run into the situation where the fired brass dimension is less than then when the die is in contact with the shell holder. Even though the cases chamber easily you may want to check your resized cases with a case gauge. Also, check to see if your die is screwed in far enough to remove the spring from the press.
"Emergencies have always been the pretext on which the safeguards of individual liberty have been eroded" - F.A. Hayek