technically the laws prohibiting a firearm in your vehicle in NLV and boulder city are preempted by state law
NRS 244.364, NRS 268.418, and NRS 269.222 state that except as otherwise provided by specific statute, the legislature reserves to itself the right to regulate the transfer, sale, purchase, possession, ownership, transportation, registration and licensing of firearms and ammunition in Nevada, and that no county, city or town respectively may infringe upon these rights. These laws specifically allow localities to regulate the unsafe discharge of firearms, and they also allow Clark County to maintain handgun registration. However, one must be in Clark County for 60 days before registration is required. Also, per NRS 407.0475 the Nevada Division of State Parks may not enforce regulations more restrictive than the state law with regards to firearm possession and self-defense.
if I ever got busted for that I would fight it tooth and nail till either the case was thrown out or the law overturned and then sue for unlawful arrest and detention and whatever else I could sue for. So far I've never been stopped in NLV and of the times I've been stopped in NV I've only once been asked about what weapons I had in the vehicle by some rookie state trooper near alamo and I suspect he wouldn't have asked if I hadn't told him I was duck hunting.
In short you could beat the rap but not the ride and it would be an expensive and lengthy process.
Don't get pulled over with a blunt in your mouth and a stolen glock on the passenger seat and I think you'll be good to go.