Stallones,
As you can see from the link about the lady at the counter was absolutely correct. You cannot ship from a UPS Store.
You either have to have a daily pickup account or go to one of their central distribution places "Customer Centers" Usually one per region in a very out of the way place... You cannot go to one of the convenient "UPS Stores" with a gun...
Thats the rules. USPS is always best IMHO.
If the gun gets damaged you will have a very hard time collecting seeing as how your shipment violated UPS's stated policy. (Ask Steve A...)