distra, understand this one tidbit about the '86 Firearms Owners Protection Act, safe passage clause: The FOPA provides an "affirmative defense." That means, if a state or locality arrests you and charges you for violating their local laws by possessing a firearm they don't allow while you're traveling through -- WHEN you get to court you may present your case that you were operating under the FOPA guidelines and the court (under federal law) must accept that reason (if you were indeed following the FOPA rules) and release you.
FOPA doesn't do anything at all to keep a state from arresting you and taking you to trial. They just can't convict you. Another way to say that is, "you can beat the rap, but not the ride."
A couple of states (NY is unfortunately, one of them) have a reputation for pushing this and dragging people through trial even though they know they can't convict. They do it just to make a point. It will cost you thousands to get through it, plus the little inconveniences of arrest, seizure of property, etc.
Long story short, follow FOPA and drive nice and steady -- not too slow, not too fast -- and don't stop for anything but gas and potty.