I'm kinda ready for bed right now, and I do this all the time, so I must confess that I did not read all the posts. There was some bad info in some of the first few though...
They changed the laws a few years back, the Airlines are no longer ALLOWED to put the "steal me" tags on the cases. The "unloaded" tag now goes INSIDE the locked container with the weapon.
Furthermore, you do not have to have metal cases, nor cases at all... BUT, the guns do have to be in a locked container... Ie- you could put them in your softsided luggage with one of those aluminum foil zipper locks and you would be in compliance.
What I generally do is put pistols inside a lockable pistol case, then put the whole case inside a bigger piece of normal luggage.
When it comes to rifles, I have to "bite the bullet" and use regular metal gun cases, with locks, and just cross my fingers that the cases don't walk out of the airport without me.
The FAA puts out the regs, so almost every Airline abides by them. Some counter personnel will be more comfortable with it than otehrs. Often the counter person will not even want to "inspect" the firearm to ensure that it is empty (as they are supposed to do), so I usually make a big show out of showing them, making sure that everyone around me sees an hears the gun being cycled.... I think of it as a "firearms awareness" opportunity.. as in : Hey, look even people who fly own guns, not just guys in seedy vans driving cross-country!
you'll have to keep the ammo in a seperat piece of luggage, and the ammount you can have is determined by the wieght. But, I have never been asked to show them the ammo, nor provide the total wieght of the rounds I was bringing along.....
Don't be intimidated, and good luck.
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-Essayons