[Unclenick]

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It was discovered by target shooters, fifty or sixty years ago, that separately crimped lead and cast bullet loads were more accurate. Combining seating and crimping of these bullets shaves lead. It can even create a small amount of bulge distortion in soft swaged bullets when the seating ram is fighting the crimp's grip on the bullet during the last few thousandths of the seating stroke. The shaving also creates added metal fouling that helps gum up a chamber (the kind of problem lead removing revolver chamber reamers were created to solve).

Jacketed bullets are less problematic and will work better with the single step seat and crimp operation. Nonetheless, separate crimping still gives you options like the the taper crimp dies for lead or the Lee Carbide FCD or, if you need a strong roll crimp for a heavy caliber in revolver, the excellent Redding Profile Crimp die.

If you feel you don't want or need to crimp separately for what you are loading and shooting, consider moving seating and crimping in one step to the last station on the Dillon, and use a powder check die in the third position. That can save you some grief on occasion.