Quote: I think "magnum" in this case means mainly the action size. Both .400/350 (rimmed) Rigby and .350 Rigby (rimless) were build in Mauser magnum actions.
That is true, but generally, when the term "350 Rigby magnum" is used it is in reference to the rimless cartridge. Rigby actually called it their 350 Magnum but I don't think they ever did with the 400/350 rimmed version except maybe the 350 No.2 loading but I would have to look at period Rigby literature to be sure.
-------------------- He who lives in the past is doomed to enjoy it.