Probably a stupid question, but here goes:

Just got a Redding Form & Trim die for .257 Wby Mag. It didn't come with any instructions--guess it's supposed to be simple enough that you need no instructions. However, I'm not sure what the proper way to set it up is. Do you turn it until it contacts the shell holder and then back off a half turn and that sets it for the correct length or do you have to place a case that is the correct length in the shell holder and then adjust the die down in the press until the case mouth is even with the top of the trim die?

If your using it as an intermediate step for reforming 7mm Rem Brass to .257 Wby brass, would you adjust the die until it touches the shell holder and back it off a half turn, or would you turn it down a 1/4 or half turn more?

I've been to the Redding website but could find no instructions.

I haven't formed .257Wby, but when forming .30 Herrett (which is a one step form, then trim, then fire form job). I adjust my form die until the case is a snug fit into the chamber of my Contender. By that I mean that once formed, and trimmed to length, the action just closes on the new brass. That minimized headspace on the new brass for fireforming. I would expect that your dies work the same way, and that the first forming will form a shoulder in the neck of the brass to headspace on, for final fireforming.