I use the Lee faactory crimp die on magnum-level handgun loads. It produces a stronger crimp than the taper crimp in a typical bulletseating die.
Attempting to apply a heavy crimp at the same time as seating a bullet causes a bulge to form in the case just below the crimp. This bulge is sometimes large enough in diameter to not allow the round to chamber in the cylinder. This problem is cured by using the Lee factory crimp die.
You can also minimize the bulge to some degree by crimping with regular bulletseating dies if you seat and crimp in separate steps. Using two separate seating dies makes this easier by adjusting one for seating only and the other for crimping only.
