The "UPS store" located in the strip shopping center next to Publix and Great Clips will not accept a firearm, no if and or but. The owner will have to take it to an actual UPS facility IF one already possess a shipping label issued by the factory service department.
Example, UPS and FEDEX won't accept a firearm that a private person (me) sold to a buyer on Gunbroker, even if the seller is shipping the item to the buyer's FFL. I had to ask my favorite gun store to ship a handgun to my buyer's FFL. It's not an ATF regulation, it's the carriers new policy.