As near as I can tell, informing UPS that you are mailing a firearm is like telling the WaWa clerk that your Twinkie is for a wedding. Suddenly, your $1 Twinkie is now a Twinkie Wedding Cake Edition, and you’ll pay $15.99.
Something to be careful of, though — when you go to UPS and tell them that it is a firearm, they will repeatedly try to get you to say that it is broken or otherwise damaged. I can only assume that they believe that this will get them off of the hook if they actually damage the item, or even lose it.
And once you’re done with that nonsense , then you hand them a king’s ransom so that they can then try to lose or damage your stuff.