As of the 1st April the law in NJ says that purchases of handgun ammunition needs a FID, to purchase in NJ.
NOT any other ammunition as you can see from the relevant bit below.
2C:58-3.3 "Handgun ammunition" defined; sale, purchase, etc., regulated; violation, fourth degree crime.
1. a. As used in this act, "handgun ammunition" means ammunition specifically designed to be used only in a handgun. "Handgun ammunition" shall not include blank ammunition, air gun pellets, flare gun ammunition, nail gun ammunition, paint ball ammunition, or any non-fixed ammunition.
b.No person shall sell, give, transfer, assign or otherwise dispose of, or receive, purchase, or otherwise acquire handgun ammunition unless the purchaser, assignee, donee, receiver or holder is licensed as a manufacturer, wholesaler, or dealer under this chapter or is the holder of and possesses a valid firearms purchaser identification card, a valid copy of a permit to purchase a handgun, or a valid permit to carry a handgun and first exhibits such card or permit to the seller, donor, transferor or assignor.
It is only binding on "bricks and mortar" retailers in NJ and does not affect on line purchases from out of state suppliers EXCEPT a few vendors (Midway for example) out of an abundance of legal cowardice/caution are restricting handgun ammunition sales to NJ until they implement the same "fax and keep a copy of the FID" process as they already do for Illinois residents.
This also does NOT affect reloading components.