At the SHOT show Hesse had a .223 pistol that, unlike PO, uses a lot of standard AR parts. IF it is not as ... questionable ... as some Hesse stuff, I was wondering if it would be
a) legal; and
b) technically possible
to put a 10" barrel on it for acceptable ballistics. There's only an ounce or two leeway, so that barrel would have to be turned mighty thin ...