Every book I've looked at suggests (for all but carbide dies) screwing the sizing die down until it touches the top of the shell holder with the ram raised, then lowering the ram and screwing the die down another half turn or so. The idea seems to be to ensure that the cartridge is completely and fully home.
The extra bit of turn to the die after contact with the shell holder takes the play out of the presses pins and linkage, which would show up as space between the shell holder and die, if you put a piece of unresized brass in the press.
Don't overdo the extra die turning, feel when the play is gone in the cam over stage. Too much and you may bend things. Carbide is more brittle and the extra pressure could crack the sizing insert.
NormB
NormB