Check out this site! Also keep in mind the 15 round mag rule. Preban or not, a magazine capable of holding more than 15 rounds are illegal unless they are blocked to 15 rounds.
http://www.homestead.com/njccw/njgunlaws.html
"A semiautomatic firearm should be considered to be "substantially identical', that is, identical in all material respects, to a named assault weapon if it meets the below listed criteria:
A. semi-automatic rifle that has the ability to accept a detachable magazine and has at least 2 of the following:
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; and
5. a grenade launcher;"