Again, the best thing to do is ASK AN ATTORNEY.
Every single state has different laws and requirements for possession, ownership, purchase, transfer, registration, carry/transport, GUN-SPECIFIC requirements, etc. etc. etc.
For instance, Texas does not require registration of firearms, so if you purchase from an individual it is "paperless" and legally so. In California, you still have to register the gun.
In Texas, IT IS MY UNDERSTANDING that you can transport a gun in your vehicle fully loaded if travelling overnight and going across multiple counties (of course, I also have a carry permit so I can carry on my person). In Illinois, it is my understanding that all weapons must be unloaded and that EVEN MAGAZINES MUST BE UNLOADED EVEN IF NOT IN THE WEAPON.
So, consult your favorite attorney.
And no trolling please.