Take a look at the States you'll have to drive through on a road trip...Geo
Geo has a point. The guns could have been gifted to the son when he still lived with his Dad, and Dad is merely taking his son's guns to him. Nothing illegal about that, or for the son to go back to his Dad's house to get his guns.
But where the problem lies is in the remote possibility that he may be stopped in one of several states controlled by Liberal Left anti-gun Democrats. Although it is not illegal to transport long guns across the country as long as they are secure and unloaded, most Democrat politicians have nothing better to do than harass law abiding citizens for the crime of exercising their 2nd Amendment rights. (Some localities may have stricter laws, especially those controlled by anti-gun Democrats) This is not opinion... it is a proven fact. It makes you wonder why any gun owner would be stupid enough to vote for those who willfully infringe upon their rights.