Nevada State Law is silent on motor vehicle carriage of firearms. Any law-abiding citizen may carry a handgun, loaded or unloaded, in their vehicle.
Some cities like North Las Vegas and Boulder City have "Deadly Weapon" laws, and you may be cited or arrested if you pass through their jurisdictions with a gun in the vehicle.
7-1-3: Discharging Firearms, Air Guns:
No person except a sheriff, constable or police officer shall fire or discharge any firearms or air guns of any description within one thousand (1,000) yards of any building, street, sidewalk, alley, highway or other public place or have any firearms or air gun in his possession within one thousand (1,000) yards of any building, street, sidewalk, alley, highway or public place unless it is unloaded and knocked down or enclosed within a carrying case; provided, that this Section shall not prevent the maintenance and use of duly supervised rifle or pistol ranges or shooting galleries authorized by the City Council. This Section shall not prohibit the stocking of firearms by duly authorized dealers in the same.
North Las Vegas
9.32.080 Deadly weapon prohibited in vehicle--Exceptions.
It is unlawful for any person to have in his possession in any automobile, truck, motorcycle, or any other type of vehicle any dangerous or deadly weapon, but this restriction shall not be deemed to prohibit the carrying of ordinary tools or equipment carried in good faith for uses of honest work, trade or business, or for the purpose of legitimate sport or recreation.