Well, if you screw down the die all the way, then it's a bit of a lottery as to how far you push back the shoulder. I would use a Stoney point gauge to measure the shoulder datum and screw down the die until you've pushed the shoulder 1-2 thou...
...Or, the easy way is to get the Redding competition shell holder set, you get a set of 5 which are designed for you to screw the die until it touches the shell holder except that each shell holder is 2 thou deeper than the next... So you swap shell holders until you've pushed the shoulder back enough.
JMHO