Some dies sets let total reloading with three dies. Some others could demand a fourth die with the taper crimp. Taper crimping, rather than roll crimping, need to often be done With all the 9mm. The under pics and facts are from a super in-depth write-up from Blessed Gunner in https://9mmprojectile86306.tusblogos.com/36653883/9mm-reloading-brass-an-overview