it makes my head hurt as to how many 9mm carbide dies RCBS, lee, Hornady, etc, have sold and how many billions of rounds have been sized with those dies and without any lube. I think you can ignore any worries about whether the die leaves a straight or taper. just set the sizing die so the shell holder does a bit of a cam over just like the instructions you got with the die. this step (at least)in reloading isn't rocket science. Save that for powder charges and projectile choices.