You can do that with the Mashburn too I believe... Any thoughts on just running .300 Win Mag brass through a 7 RUM or 7RSAUM sizer in order to form brass?

Sounds like at least two people are able to form brass by way of running .300 Win Mag brass straight into the 7mm Mashburn dies before fireforming. Gotta be gentle though.

"For some unfortunates, poisoned by city sidewalks ... the horn of the hunter never winds at all" Robert Ruark, The Horn of the Hunter