Weather you need a Factory Crimp Die really depends on your guns.
My rugers will eat any ammo, FCD or not.
The carry pistols I have owned on the other hand, will not.
I had a kel-tec 9mm with a very tight chamber that would not go into battery if a round was out of spec at ALL.
And before I got a FCD for my .380, I would experience about 1-3 out of 100 rounds that would not allow my gun to go into battery, and occasional light strikes caused by the gun going into battery far enough to fire, but then the cartridge would move forward a bit on the first pull, absorbing the FP energy and requiring a second pull to fire (the ones I didn't eject and take home to find out why they didn't fire) None of the problem rounds would fit in my loaded case gage.
Since getting the FCD, the gun has been 100%, no failures.