And if you don't have a proper heavy-duty press to form them with ( at the time my little Lyman Spartan C wasn't up to it) use a vice. Lube the case insert it into die , decapping rod removed, slip shell holder on case rim as a stop, then slowly close the vice jaws, making sure everythings lined up , Of course you have to use a rod and mallet to drive the case out of the die .
I once formed 7 X 57 cases out of 30-06....I was young and had thousands of once fired military cases. Still not a great idea.
Gary