Like I said about ultra conservative attorneys, Nappen falls into that category.
When pressed, he will confirm it is not illegal, just not advised because a cop or a prosecutor may claim that a loaded magazine is a loaded firearm.
To quote our local gestapo in https://njsp.org/firearms/firearms-faqs.shtml
6. How do you transport firearms?
Firearms shall be carried unloaded and contained in a closed and fastened case, gunbox, securely tied package, or locked in the trunk of the automobile in which it is being transported. If the vehicle does not have a compartment separate from the passenger compartment, the firearm and or ammunition shall be in a locked container other than the vehicle's glove compartment or center console and kept farthest from the driver.
As a precaution, ammunition shall be transported in a separate container and locked in the trunk of the automobile in which it is being transported. Ammunition magazines may remain loaded during transportation and shall be carried separate from the firearm.
To quote Evan Nappen: "The exemptions in 2C:39-6g require that your gun be unloaded. The ammunition can be right next to your gun, even in the same box case. But don’t have it loaded in any magazines because if the magazine is loaded, they will claim the gun is loaded."