Some time ago, Les Bauska had some Ruger #1-type actions cast large enough to handle the .600 Nitro as he was quite taken by the Farquarson-type single-shot rifles of the 1900 period.
: I wonder if his son has any of these action left?? They are out of reach for me (CDN), but not for guys in the States. He should still be in Kalispel, Montana, I believe.