CH, Your Dillon die set should be a 2 die set as you are dealing with a bottle neck rifle style cartridge. The sizing die should have the expander incorporated in it along with the decapping rod inside the die. When you run a 10 mm case through the die and withdraw it, the case is neck expanded by the expander button on the decapping rod. Were I reloading them, I would use a Lee Universal expander die to put a slight flare in the case mouth to ease bullet seating. Then I would seat the bullets in one step and crimp in another. I've been loading the 357 Sig since it appeared in 1994 and have learned a lot about bottleneck pistol cartridges. The 9x25 is just a lengthened 357 Sig. I suspect the folks at Dillon could answer any and all questions in reference to their dies and loading the 9x25. Bob! BTW, what pistol are you shooting it in? :wink: