For a non-trued action, I'm fairly certain I PREFER a two piece bolt (i.e. Savage's floating bolthead). I like the idea a heck of a lot better than a rear lock-up, that's for sure. In the words of Jiminy Cricket, "let the chamber be your guide". The margin for error is much improved when you're talking about a front end lock up with a floating bolthead. A small deivation on center at 3-4" away from the chamber (rear lock up) is a pretty big variance at the cartridge base(relatively speaking).

Two-piece bolt designs sure seem to work for AR's too.