How short can you get away with, legally?  That would be from muzzle end to butt stock end.

Thanks!

Overall length is measured with collasping/folding stocks extended.  The barrel is measured from the face of the chamber.  NFA rules are a >16" barrel and a >26" overall length.  Thus, with a folding stock (for example, a Thompson Contender or NEF break action), you could have a gun only 16" long with the stock closed, as long as the gun was 26" long with the stock open.  Any less than either of these measurement and you have a short barreled rifle. Postban/preban rules still apply for semi-autos.

Kharn

This would not be for an AR rifle.  It is one of those 'Bullpup' configurations that you can do to an AK rifle.  

Anyway, thanks for the information!  [:)]