Ive noticed the American made 9x19mm (Parabellum, Luger) has a slight taper at the base of the case. Ive had trouble getting them to fit in my Medusa.. A couple of days ago I got some loose Seller & Bellot 9mm Luger from a friend and they fit beautifully... Looking at the cases I noticed the the Seller & Bellot doesnt have the taper at the base and is more of a straight-walled case...
Why is this? Why do the American 9mm's taper and foreign ones do not? Does it not really matter? (except in my Medusa)

Would the Lee Factory Crimp die get rid of this taper? Can the crimp part be removed so I could resize loaded ammo, or use it on 9x23 (I have a box but it has the same taper as 9x19, and doesnt fit the Medusa)