Fireforming k-hornet

[Cossack]

I do it in several wildcats where the headspace/pressure is too risky.

It's likely that necking up and then necking back down a Hornet case would work the brass even more than straight fireforming a standard case.
You're likely to spoil some cases necking up enough to create the false shoulder. Other than the time, possible increased work-hardenting of the brass...which you would still have to fireform to max accuracy.... I see no problems with doing it, tho.