The only reason I'd use a 700 action is for a SA varminter... I think I'd go 700, though it certainly doesn't matter either way... as Dober points out, it's the trigger not the action.
Bob, is the 6xC essentially a 6mm-250/3000?
It can be formed out of 22-250 cases, the neck is expanded to 6mm, the shoulder is pushed back and the body taper is reduced.
