Notwithstanding any state or local law, a person shall be entitled to transport a firearm from any place where he may lawfully possess and transport such firearm to any other place where he may lawfully possess and transport such firearm if the firearm is unloaded and in the trunk. In vehicles without a trunk, the unloaded firearm shall be in a locked container other than the glove compartment or console.
Source
NRA-ILA Federal Gun Laws
Loaded mags will generally be OK IF they are not in the gun or near it. In other words, loaded mags in a seperate locked container (doesn't have to be locked, but locked means the cops can't open it without a warrant. Why make it easy?). However, in CA or similar freedom-hating states some activist judges have interpreted loaded mags as being the same as loaded guns. The ridiculousness of that position will be shown the first time they try to bust someone who has loaded mags in the car but no actual firearms.
I also have an SUV. A trunk IS a locked container. Since we don't have one we have to use locked gun cases or bags.
A police officer can search without permission "anything within the immediate control of the driver" for his own protection. Open bags on the front seat, glove compartment. Anything else they need your permission, so he'll have to send you on your way unless he has reasonable suspicion to arrest you. So if you smell like pot, or are wearing a roach clip as jewellery, or he sees blood all over the back seat, well you get the picture.
When driving with guns I tend to load the gun cases first, then put the rest of our luggage on top. You KNOW if you are pulled over they will eyeball the back of the car as they walk up to the front window, so just make it harder for them to find an excuse to harass you. (However, if you are driving in an area with lots of gun racks with actual guns in them
then this probably isn't necessary. I live in California though, so I don't even have an NRA sticker).
If you are driving through any National Parks you should be aware that there are some real antis in the park service. They have interpreted the law in an odd way. 36CFR2.4 states that:
unloaded weapons may be possessed within a temporary lodging or mechanical mode of conveyance when such implements are rendered temporarily inoperable or are packed, cased or stored in a manner that will prevent their ready use
Now see how this is interpreted:
In order to transport weapons through NPS areas they must be dismantled and adequately cased or packed in such a way as to prevent their use.
Source
NPS Weapons regulations
I don't know if anyone has ever been busted on weapons charges in a NP because of this overzealous interpretation, but I doubt it would make the evening news, so it is possible. More than likely it would only happen if the Park Service were looking for enhanced charges to hit someone up on. They also say you are supposed to declare weapons when you enter the park, I did it once and the sweet young lady smiled and said "that's nice" and handed me my maps and receipt. No paperwork, no red tag to hang off your rearview mirror. Therefore I say don't bother. If it becomes an issue later I will say I told the person at the entrance.
Remember, I am not a lawyer, I only play one on the internet. So use common sense.
madkiwi