You can try it with the bar set wherever it is and see what the dropped charge is. Then turn it in one turn (CW) (this increases the charge) and weigh it again. That will give you the approximate change per turn. Comparing that to what you dropped, you can estimate the number of turns, in or out to get where you want. Once you are there, mark it. I have a stack of Dillon powder slides, marked with a sharpie marker as to weight of what (like 7.0 unique, or 4.2 231) so I can substitute bars depending on the cartridge I'm loading, and not go through the process every time I change caliber or load. Still want to double check your load with a powder scale every time you start up, especially necessary with a new can of powder, as it may change from lot to lot.