The last time I checked, NJ includes muzzleloaders in the definition of firearms...BB guns, too. In the early 1970's, NJ had an especially nasty, anti gun Attorney General..name of Sills. As the BP craze grew, he so interpreted the then-existing statutes...he lost a case in the state Supreme Ct. and that had the effect of throwing bp guns into a limbo that lasted for about 14 or 15 months. I scraped together my pennies and bought my Euroarms .36 Remington during that time period, just because I could. When Sills stopped his hissy fits, the legislators gave him a bill that included muzzleloaders as "firearms"...but, as a sop to shooters, they also included BB guns, air rifles and pistols and CO2 guns as "firearms"...prior to that they'd been on the same "banned weapons" list as sawed off shotguns and machine guns.
While it let folks get bb guns then, the effect now is that a chap shooting a Red Ryder in his back yard is guilty of discharging a firearm under the no discharge ordinances that many municipalities have. 20 years ago, my son shot himself in the hand with a .177 bb from a crossman rifle...today, I'd be looking at five years in prison for providing a firearm to a minor, and for his 'gunshot' wound...even back then, it was reported to the police as a gunshot wound...luckily, we were still rural enough to have the kind of cop who said, "oh, for pete's sake..I have a bb in my foot to this day..." Hank