The below listed information is from a document on AWs I saved some time back. As per forum rules on copyrighted materials, I will credit this text as coming from BATF as a source document, although I am not 100% certain BATF is the original source.
Definition of "semi-automatic assault weapon":
(A) Any of the firearms, copies, and/or duplicates of the following firearms (in any caliber):
(1) Norinco, Mitchell, and Poly Technologies Avtomat Kalashnikovs (all models),
(2) Action Arms Israeli Military Industries UZI and Galil,
(3) Beretta Ar70 (SC-70),
(4) Colt AR-15,
(5) Fabrique National FN/FAL, FN/LAR, and FNC,
(6) SWD M-10, M-11, M-11/9, and M-12,
(7) Steyr AUG,
(8) INTRATEC TEC-9, TEC-DC9 and TEC-22, and
(9) Revolving cylinder shotguns, such as (or similar to) the Street Sweeper and Striker 12;
(B) A semiautomatic rifle that has an ability to accept a detachable magazine and has at least two of the following components:
(1) A folding or telescoping stock,
(2) A pistol grip that protrudes conspicuously beneath the action of the weapon,
(3) A bayonet mount,
(4) A flash suppressor or threaded barrel designed to accommodate a flash suppressor,
(5) A grenade launcher;
(C) A semiautomatic pistol that has an ability to accept a detachable magazine and has at least two of the following components:
(1) An ammunition magazine that attaches to the pistol outside of the pistol grip,
(2) A threaded barrel capable of accepting a barrel extender, flash suppressor, forward hand grip, or silencer/suppressor,
(3) A shroud that is attached to, or partially or completely encircles, the barrel and that permits the shooter to hold the firearm with the non-trigger hand without being burned,
(4) A manufactured weight of 50 ounces or more when the pistol is unloaded, and
(5) A semiautomatic version of an automatic firearm;
(D) A semiautomatic shotgun that has at least two of the following components:
(1) A folding or telescoping stock,
(2) A pistol grip that protrudes conspicuously beneath the action of the weapon,
(3) A fixed magazine capacity in excess of 5 rounds, and
(4) An ability to accept a detachable magazine.