Expanding on Tehano's post; a lot depends upon whether you are pushing the shoulder back and the cases you are reforming from.
I form 219 Donaldson Wasp from 30-30. The 30-30 case walls become the Wasp necks. This is an extreme reforming. It's a given I will have to turn the necks before I fireform the case. In 20 years I've yet to run into a "donut" at the base of the neck with Winchester or Nosler brass as others have, but I bought a reamer bit for my Forster trimmer just in case.
