It is not legal, the Hunters book is wrong, look at the statues the only thing allowed is a suppressor. A SBR is still considered a WMD and is not legal.
§ 113-291.1. Manner of taking wild animals and wild birds.
(c) It is a Class 1 misdemeanor for any person taking wildlife to have in his possession
any:
(1) Repealed by Session Laws 2013-369, s. 23, effective October 1, 2013.
(2) Weapon of mass death and destruction as defined in G.S. 14-288.8, other
than a suppressor or other device designed to muffle or minimize the report
of a firearm that is lawfully possessed by a person in compliance with 26
U.S.C. Chapter 53 §§ 5801-5871.
§ 14-288.8. Manufacture, assembly, possession, storage, transportation, sale, purchase,
delivery, or acquisition of weapon of mass death and destruction; exceptions.
(c) The term "weapon of mass death and destruction" includes:
(1) Any explosive or incendiary:
a. Bomb; or
b. Grenade; or
c. Rocket having a propellant charge of more than four ounces; or
d. Missile having an explosive or incendiary charge of more than
one-quarter ounce; or
e. Mine; or
f. Device similar to any of the devices described above; or
(2) Any type of weapon (other than a shotgun or a shotgun shell of a type
particularly suitable for sporting purposes) which will, or which may be
readily converted to, expel a projectile by the action of an explosive or other
propellant, and which has any barrel with a bore of more than one-half inch
in diameter; or
(3) Any firearm capable of fully automatic fire, any shotgun with a barrel or
barrels of less than 18 inches in length or an overall length of less than 26
inches, any rifle with a barrel or barrels of less than 16 inches in length or an
overall length of less than 26 inches, any muffler or silencer for any firearm,
whether or not such firearm is included within this definition. For the
purposes of this section, rifle is defined as a weapon designed or redesigned,
made or remade, and intended to be fired from the shoulder; or
(4) Any combination of parts either designed or intended for use in converting
any device into any weapon described above and from which a weapon of
mass death and destruction may readily be assembled