That's something I've wondered or the last 15 years or so. How much crimp is correct?
I've just done it by feel and made sure the case mouth was "bumped" into the crimp groove. Of course, some crimp groove are larger and deeper than others depending on the bullet.
I've gotten by, as have others, but if anyone had a scientific method for measuring and applying a roll crimp to revolver cartridges, I'd sure like to hear it.
