I have a hornady 270 wsm set and the seater stem would put a dent/ring around the bullet where it was contacting the bullet during seating. I put the seater stem in my drill and lightly sanded and polished the seater plug and the problem still remained. I called customer service and they told me to do the same thing I already did. A little better, but still have the ring/dent.
I see they also sell an "amax" seater stem for some calibers for $12. I'm not sure why they wouldn't make a seater stem that works on all bullets. I have used my "cheap" Lee seater dies and have never had a problem with the bullets being dented and COAL consistency and runout are the same or better than the Hornady dies.
Just my experience. Maybe I got a dud seater die.