https://www.govtrack.us/congress/bills/103/hr4296/text
30-A listed the items that cannot be "copies or duplicates"
30-B defines what would be 'semiautomatic assault weapon' if it had the related features
I believe only (ii) would fit the products sold in MA.
‘(30) The term ‘semiautomatic assault weapon’ means--
‘ (A) any of the firearms, or copies or duplicates of the firearms, known as--
‘ (i) Norinco, Mitchell, and Poly Technologies Avtomat Kalashnikovs (all models);
‘ (ii) Action Arms Israeli Military Industries UZI and Galil;
‘ (iii) Beretta Ar70 (SC-70);
‘ (iv) Colt AR-15;
‘ (v) Fabrique National FN/FAL, FN/LAR, and FNC;
‘ (vi) SWD M-10, M-11, M-11/9, and M-12;
(vii) Steyr AUG;
‘ (viii) INTRATEC TEC-9, TEC-DC9 and TEC-22; and
‘(ix) 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 2 of--
‘ (i) a folding or telescoping stock;
‘ (ii) a pistol grip that protrudes conspicuously beneath the action of the weapon;
‘ (iii) a bayonet mount;
‘ (iv) a flash suppressor or threaded barrel designed to accommodate a flash suppressor; and
‘ (v) a grenade launcher;