I am using a Redding 45 Colt bullet seating die, to crimp a bullet cast from 20:1 alloy in a Lyman 452664 four cavity mold in Hornady brass.
I apply maximum crimp with the die body turned down to touch the shell holder.
When I wipe off the bullet to remove lube that has squirted out of the crimp groove up the side of the bullet there is hair thin ring of brass on the paper towel mixed with the lube.
Why am I shearing off brass? Too much crimp?
The finish crimp looks good with the case mouth tucked under the upper edge of the crimp groove to prevent the bullet from being pushed back into the case.
Fired cases still show a slight roll in of residual crimp, which I thought would or should have been ironed out flat parallel to the case wall by the passage of the bullet.
I do use a LEE de-burring tool on the case mouth for a minimalist approach to keep the brass case mouth near original thickness.