Here is the exact wording of the law:
Title 18
United States Code
Chapter 44
921(a) The term 'semi-automatic assault weapon' means-
(A) any of the firearms, or copies or duplicates of the firearms in any caliber known as
1) Norinco, Mitchell, and Poly Technologies, Avtomat Kalashnikovs (all models);
2) Action arms Israeli Industries UZI and Galil;
3) Beretta AR70 (SC70);
4) Fabriquie National FN/FAL, FN/LAR, and FNC;
5) Colt AR-15
6) SWD M-10, M-11, M11/9, and M-12;
7) Steyr AUG;
8) Intratec Tec-9, Tec DC-9, and Tec-22 and
9) revolving cylider shotguns, such as (or similar to) the Street Sweeper and Striker 12;
(B) a semi-automatic firle that has tha ability to accept a detachable magazine and has at least two of
1) A folding or telescoping stock
2) a pistol grip that protrudes conspicuosly beneath the action of the weapon
3) a bayonet mount
4) a flash suppressor or threaded barrel designed to accomodate a flash suppressor; and
5) a grenade launcher
Maybe this will help clear things up.