Re: ?To nut or not to nut?
If it were me, I'd true the action, or at least machine the receiver front face square to the bolt bore, get a precision ground recoil lug, and use a shouldered barrel with out the nut. The reason is shouldering the barrel to contact the recoil lug directly eliminates any misalignment that might be built into the nut.
The pro is elimination of a potential source of misalignment and thus possibly better accuracy. The con is that the barrel will only fit that particular action. You pick your pony and take your ride.
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." R. Feynman. (Last sentence of the Feynman appendix to the Space Shuttle Challenger Report.)