There is a special rotating star shaped crimping head that's used to crimp the blank. It starts and as it rotates it closes up until the crimp is tight. If it came straight down it'd bell out the lower part of the neck. If you think that .303 crimp is pretty slick, you should see .50 Browning. It's a mean machine that does that, believe me!

The trouble with blank is that it makes a one way trip