Only a thought, maybe consider turning the rim last so that you can use a standard shell holder to work the brass. Maybe, once you swage the web, you can run it in a regular press with dies for other cases to step down the thin wall part of the brass. Maybe, do a chamber cast, just in case you don't have to reduce things as much as it might seem. Best of luck with it.

Since your so determed to swage the '06 cases, I'll add how I do my head re-sizing.

I've made 32/35 from 30/30, that's only .018 reduction, 30/40 to 32/40, reduced .041 and my last one was 357 Mag to 32/20, a .027 reduction.

Your reduction will be .120 so, I would do it in 3 steps of about .040. I do almost all my case forming in a 2 ton arbor press, that I reamed a .501 hole in the ram, with a 1/4x20 set screw to hold the tools. The arbor press, because it's faster to make the dies, using just a 1/2" shank, instead of threading them 7/8x14. It also has a 1/2" plate bolted to the bottom with a 1/2" hole for CH univeral shell holder. I'll add a picture of it, set up for case forming. I also punch my wads with it and many other operations.

The first operation would be to make a die with a hole about .040 under the solid head, closest would be .422. Radius and polish the mouth of it, at least .06R and run the die down to the solid head. Chuck it and turn the head to .424/.426, so that you don't machine the brass forward of the solid head.

Continue at convenient increaments, until you get the head size you want. If done that way, you won't thin the brass to much at the head to web junction, only the solid case head.

Frank