Here's the UPS written policy:
http://www.ups.com/media/en/terms_service_12312007.pdf
And the part that counts, notice the bold:
J. Firearms and Ammunition
UPS accepts packages containing firearms, as defined by Title 18, Chapter 44, and Title 26, Chapter 53 of the United States Code, from and between licensed importers, licensed manufacturers, licensed dealers and licensed collectors, as defined in Title 18, Chapter 44 of the United States Code, law enforcement agencies,
from and between persons not otherwise prohibited from shipping firearms by federal, state or local law, and when such shipment complies with all federal, state and local laws applicable to the shipper, recipient and package. The shipper must use Delivery Confirmation Adult Signature Required service for each package containing a firearm, including handguns. UPS, in its sole discretion, may require the shipper to select a UPS Next Day Air Service for any package containing a firearm.
Handguns, as defined by 18 U.S.C. § 921, will be accepted for transportation only via UPS Next Day Air Services. Firearms, including handguns, will not be accepted for transportation via UPS Drop Boxes, Internet Shipping, in response to a request for On-Call Pickup Service, or when presented for shipment at locations of The UPS Store or any Third Party Retailer. Small arms ammunition, as defined in 49 C.F.R. § 173.59, will be transported only when packaged and labeled in compliance with 49 C.F.R. § 172. Firearm parts, which do not constitute firearms as defined under federal law, including without limitation Title 18, Chapter 44, and Title 26, Chapter 53 of the United States Code, and which otherwise comply with federal, state, and local law, will be accepted for transportation. UPS Returns Services are not available for packages containing firearms. Firearms, including handguns, and firearm parts are not accepted for shipment internationally. For more information, access
http://www.ups.com/content/us/en/resources/service/terms/firearms.html, or contact UPS.