Even in New York State, a pre 1899 mfg 12ga shotgun meets the 'Antique Firearm' definition and requires no FFL involved in it's transfer.

There's no NYS law contrary to the Fed Antique Firearms definition when it comes to long guns.

... there is however with pre 1899 cartridge handguns in NY State.

As always,,watch those local and State laws..
Some municipalitys may have their own laws regulating possession, sale, etc.