Thanks Lou, very useful summary. The cutting of the case worries me a little - is this using a fine bladed hack saw and a form die?
Otherwise, after a lot of searching, the Teppo Jutsu 500 Phantom shows how that case was made from 500 Jeffrey ==>
http://www.teppojutsu.com/.
The Jeffrey case seems to be a bit more versatile than either the 338 Lapua or the Weatherby.