Wonderful LEE came up with a very good idea .... Factory Crimp. Then they abused the name.
The LEE Factory Crimp (FC) die for rifle cartridges is a collet die. That is, it closes down as the cartridge is pushed up into the die. It make four or more indentation in the case neck which act to hold the bullet in. It is not a classical roll or taper crimp but indentation in the end of the neck. It is not sensitive to the trim length of the case as long as the case OAL is greater than the minimum, whereas uniform crimping in conventional die sets are trim length sensitive.
This rifle Factory Crimp die can suffer from a common LEE malady of the use of the wrong materials in the product. Eventually the similar metals of the collet and the die body gall and upset the operation of the FC die. It takes a stone to remove the galling to extend the life of the die. This was the case in my early examples of the FC dies.
When it was time for a similar Factory Crimp die for pistol cartridges LEE used the same name and a totally different design. The FC die for pistol cartridges uses either a roll or taper crimp in this die just as does the crimping action of the original die set. But LEE includes a carbide ring at the bottom of the die that works to size the finished cartridge during the FC crimping. It is not a bad idea to assure all your handgun ammo fits you gun's chamber but why did LEE not call it something else rather than ride on the success of the rifle version.
I have both rifle and pistol FC dies and like the rifle version. The pistol version was bought without knowing its design. I'll not be buying another FC pistol version as I have never had problem with any of my pistol reloads fitting any of my guns, nor have I had any trouble with using the crimp in the seating die provided with every die set.