As far as visiting other states, California seems to be the most reasonable out of the 5 or so horror states. Aside from the assault weapon and magazine restrictions, bringing a gun into the state isn't any different than the majority of other states.
This is fairly true.
California has some complex laws for someone unfamiliar with them and how various state specific exemptions and configurations are required to possess certain types of firearms, but most title 1 firearms can manage to be possessed by someone travelling through.
There is some specific brand and model firearms banned by name, but the same or similar firearm from another brand will have a legal configuration.
Most handguns outside of a shotgun shell shooting handgun will be legal to bring with a magazine less than 10 rounds. Most pump shotguns, and most semi auto shotguns in certain configurations.
All lever action rifles. Most bolt actions with 10 round capacity limit and prohibition on .50 BMG caliber. The majority of semi auto rifles if an unlisted brand or model, and in certain configurations.
The North Eastern part of the country is much worse. You cannot even legally have many guns or classes of guns in some states without an unreasonable permit an RV traveler is unlikely to acquire.
New York state for example goes from the coast to Canada and blocks you off from everything North East of it without trying to use FOPA and going straight through with no touristy stops with locked cased firearms.
Connecticut, Maryland, Massachusetts, all make going past New York State more difficult as well as they also cannot be a destination of yours under FOPA and also are unfriendly to most out of state people with guns and no permit. So you have to go through hostile territory to reach Vermont, New Hampshire, or Maine.
That is the biggest blockade of the nation in my opinion.
By contrast California can actually be your destination and most things can be brought in some manner. Of course they keep trying to outdo themselves in the CA legislature and it gets more complex and worse all the time. Had the Governor not vetoed some recent legislation that passed all the other branches of government in CA this answer would be quite different.
