Charlie98
Member
light crimp for faster burning powders, heavy crimp for slower burning powders.
I have noticed unburned powder in the cases of IMR4227 when I didn't have a firm crimp.
That... and that...
Even with powders as 'fast' as Unique, I've used a taper crimp in lieu of a roller, but beyond that, or with heavy charges of Unique, I mash that roll crimp in.