Thread: What causes this

Appears there is a shiny mark on the top of the case mouth.
I believe they are seat and crimp dies - fine on pistol but not on anything rifle.
It's crimping the mouth as its still tring to seat projectile.
Back the die right out and wind the seater in all the way.
Wind die down until you are close to seating depth then back the seater stem out a couple of turns and wind the die in a couple. Should be well clear of the taper in the top of the die.
You can you the taper crimp to crimp, but as a separate stage after seating.