Yes - that is correct, re: fireforming.
I've gotten to using normal loads for fireforming. It's a pain in the ass to not have the brass fill out perfectly on the first shot.

A neck-up die could be made from a case mouth expander for a .40 cal. pistol die, or a .44 mag die as in my picture, the die on the left. I merely ground a slightly sharper taper to it's nose.

If your rifle chamber's headspace checks out at zero or out only 1 or 2 thou, simply necking them up in your 9.3x57 dies should be sufficient.

Some guys, to prevent any case stretching at the web, not only seat the fireform bullet into the throat, holding the case back against the bolt face but lubricate the case walls itself to prevent them from adhereing to the chamber walls as the pressure builds. If a sloppy case sticks at the high pressure spasm as-is normal, then the pushed forward case has no support from the bolt and the case sets back against the bolt, thus stretching the web of the case - exactly what we do not want.