I am 10 min from where you grew up by Watchung reservation. ( small world

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Under New Jersey law, air gun / rifle is classified as a firearm so all laws pertaining to firearm apply. Any sound suppression, treaded barrels, flash suppressors. Even a BB gun is considered a firearm. I know this because when in college my roommates friend brought a bb in PA had it in a trunk of his car. He got stopped for speeding and got his car searched. Got arrested for illegal possession of a firearm. Last I heard, his father spent a fortune trying to get him out of jail.
Get this ; slingshots are illegal in NJ
Living in NJ you really need to know your laws cuz some police officers are simply not knowledgeable and first thing they go for is arrest or minimum confiscation. I know this first hand. Had my rifle confiscated just cuz it look like” assault weapon”
I was at a local range with my CZ S200 and an off duty officer passed by and out of nowhere started asking questions “ what’s this, a PCP, better not be suppressed, let me see” I literary had to fight him off with knowledge of the law.