CPA

[Kurt]

Steve.
The difference between a case form die and a sizing die is the case form is just a couple thousands tighter then the normal full-length sizing die to allow for the brass spring back when you squeeze down the parent brass like the .45 in this case.
It would be nice if you had an intermediate die like a .44-90 or a .44-70 straight for the first pass. This would aid in keeping the possibility of dents down.
When you start forming this brass from .45-90 if this is the way your going make sure you use a good case lube. To much is just as bad as not enough.
If your going to form the cases from .45 brass I would anneal then about 1/2 way down to make them easier to size down.
Or if your going with the factory brass you might still have to get then sized down depending on the chamber