I won't use them.
I use a light Taper Crimp on .32ACP, 9MM, 40S&W and .45ACP.
All other handgun get a roll crimp .
All crimping is done is done separately from seating.
I use a roll crimp on .38-40, .44-40 & .45Colt when using the old style Black Powder bullets that have no crimping groove; (#40043, #42798 & #454190). They are made to crimp on the ogive. Never had a problem with bullets being pushed back into their cases.
I do use a light Taper Crimp for .223, .308 & .30-06 when loading those cases to be shot in a military style semi-auto.
I've fired thousands of rounds of .38-40, .44-40 & .45Colt in lever action rifles WITHOUT ever having the rounds having their bullets shoved back in their cases under recoil or magazine spring pressure.
I think the FCD is a crutch for Lee's poorly made dies.