Usually the seating die will crimp a round just fine. Minor variations in case thickness and length can effect the amount of crimp applied, but usually not significantly. If not properly adjusted, the crimp can vary from none at all, to collapsed cases. The LFCD forms it's own cannelure on bottle neck cases and bullets as it crimps. (Same for the roll crimp on revolver rounds) The crimp holds the bullet in place until pressure builds, much like seating the bullet out touching the lands. The LFCD for pistol rounds forms a proper taper crimp, the revolver die forms a proper roll crimp. All without concern over case wall thickness or slight variations in case length, from very light, to super heavy and all without ever collapsing a case. Even some of us who don't find die adjustment especially challenging, use the LFCD. I haven't found a better way to crimp.
Savage