I reform a large number of 30/06, 270, and 25/06 brass into 9.3x57.
Cases get annealed first.
I use a Lee case trimmer shell holder and lock stud in a drill press to cut the neck of this brass to ~57.5 mm by turning the brass in a drill press and using a hacksaw with a hardwood pillar on the drill press blade for the initial cut.
The brass is then run through a Hornaday® 9.3x57 size die
I built a collar for the Lee 7x57 case trim stud that is 0.280 Inside diameter and 0.366" O.D.
That centers the cutter in the formed case
The cutter and stud are mounted in a drill press and the final trim is done
This is the first attempt, it works extremely well
the next one will be made out of brass and have just a bit more polish.