I'm guessing it would have to be that way since all of the Ackleys are fireformed and the .30-30 headspaces on the rim. I'm thinking it might not do well to blow it out like the Ackleys that heaspace on the shoulder to fireform... and you might not gain as much powder space as moving the shoulder foreward... just a guess.
I'm surprised that 30-30 brass could take that kind of stretching.