I was under the impression that Federal Peaceable Journey laws would overrule that, as long as the gun and mag were separate and I didn't stop within the People's Republic during my trip.
I lived there about 10 years ago and at that time it was a bad idea to have a loaded magazine, or even bullets in the same case as the gun. If something has been changed since then, I apologize for the bad info.
I do not want to see anyone have a problem because of something that could have been avoided. We already have a long, uphill battle defending our rights.