Most die manufacturers seem to setup sizing dies by screwing die in until it touches the shellholder, then adding an additional partial turn. RCBS an additional 1/8 to 1/4 turn, Lee an additional 1/4 to 1/3 turn. These manufacturers seem confident that setting will provide a minimum headspace setting.
I have Dillon 223 carbide dies, and the instructions in the box say to screw sizing die in until it touches and back off 1/2 turn. I watched a die setup video by Dillon on youtube, and it said to screw die in until it touches shell plate. I called Dillon today to discuss the discrepancy of the instructions, and they said screw in until it touches, then back off 2 turns. With all three differing instructions, these are just initial settings, to be verified with a headspace gauge, and the final setting is based on the gauge.
Despite the variety of initial settings in Dillon instructions, it appears they don't seem to manufacture their dies with confidence in the headspace being minimum relative to contact with the shellholder like other manufacturers. Is that really what is going on or they just want more careful verification with another $40 tool? If that is the case (pun noted) Dillon dies require an additional outlay for every caliber that other makers don't require.