I have an nef .223 w/ a bull barrel. can this barrel be re-chambered for the short magnum? if so by whom? thanks

You would have to rechamber it to the Wnchester Super Short magnum because Win doesn't make a WSM in 22 caliber. You'd have to measure the width of the barrel at the chamber to see if there is enough metal there to have the safety margin.

I don't think that the NEF can handle magnum cartridges (read, pressure) at all, can it?

interesting question.

One might be insane to recommend that rechambering....but it might be safe. The WSSM is about the same pressure as a .25-06 and in a mag size bolt face the NEF might work well....Is it chambered for any magnums?

Here's where you're likely to go to pot.....the .223 rifling twist is typically 1:12 and the WSSM is fast enough to possibly disintegrate the bullets with that twist. I'm not sure what the twist rate is but you might want to check.

further the WSSM is shorter than the .223 Rem and you can't reset the barrel...it's fixed.....
Frankly the chances of this seem slight. Rechamber to 22-250 maybe.....