Crimping in a separate step can give you a more consistent COAL as well as more consistent crimp. For me with 38spc I was having chambering issues in my Colt Official Police with coated lead. The chambers are really tight. Anyway, when I got a Lee FCD the chambering issue went away. I was able to adjust the crimp to get the cases back to perfectly (or good enough) straight after belling then for seating the bullet. With the factory seating-crimp die I just couldn’t get it just right and I’d have a lot of rounds that I had to shove in to the chambers no matter how I adjusted things.
Also on bullets with a crimp ring I can more easily crimp them in to the crimp ring.
At this point I have a Lee FCD for every cartridge except .30-06 (because everyone has been out) and semi-auto pistols that don’t start with Tokarev (because I’ve got one for 7.62x25).
I haven’t seen a need for straight wall (or tapered) pistol/rifle cases. Rimmed and bottle neck, yes. I’ve generally seen an improvement.
Also on bullets with a crimp ring I can more easily crimp them in to the crimp ring.
At this point I have a Lee FCD for every cartridge except .30-06 (because everyone has been out) and semi-auto pistols that don’t start with Tokarev (because I’ve got one for 7.62x25).
I haven’t seen a need for straight wall (or tapered) pistol/rifle cases. Rimmed and bottle neck, yes. I’ve generally seen an improvement.