For those calibers, I know of 2 reasons an FCD might be useful:
1. In 40/45 for using as a bulge buster. Requires a push through adaptor. Will not work for 9mm.
2. For hollowpoints on a turret or progressive. If your seater plug is squishing the hollowpoints, it definitely helps to crimp in a separate step, so the pressure is not as great during seating. On a SS press, you can use your seater die to crimp in a separate step.
The only other time I've needed an FCD is for post sizing .38 special wadcutters. The thicker brass sometimes bulges so much at the base of the bullet, they won't chamber. The FCD fixes this. I'm not sure how accuracy is affected, but at least they'll chamber.
1. In 40/45 for using as a bulge buster. Requires a push through adaptor. Will not work for 9mm.
2. For hollowpoints on a turret or progressive. If your seater plug is squishing the hollowpoints, it definitely helps to crimp in a separate step, so the pressure is not as great during seating. On a SS press, you can use your seater die to crimp in a separate step.
The only other time I've needed an FCD is for post sizing .38 special wadcutters. The thicker brass sometimes bulges so much at the base of the bullet, they won't chamber. The FCD fixes this. I'm not sure how accuracy is affected, but at least they'll chamber.