The belief that one must notify the carrier that the item being shipped is a firearm likely comes from a statement on BATF's website that is, at best poorly referenced, and at worst, just plain false.
I'm referring to:
http://www.atf.gov/firearms/faq/faq2.htm#b9
quote:
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B9) May a nonlicensee ship a firearm by carrier?
A nonlicensee may ship a firearm by carrier to a resident of his or her own state or to a licensee in any state. A common or contract carrier must be used to ship a handgun. In addition, Federal law requires that the carrier be notified that the shipment contains a firearm and prohibits common or contract carriers from requiring or causing any label to be placed on any package indicating that it contains a firearm. [18 U. S. C. 922( a)( 2)( A) and 922( e), 27 CFR 178.31]
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The law this bit of disinformation references is at:
http://www.atf.gov/pub/fire-explo_pub/gca.htm
quote:
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922. Unlawful acts
(a) It shall be unlawful --
(e) It shall be unlawful for any person knowingly to deliver or cause to be delivered to any common or contract carrier
for transportation or shipment in interstate or foreign commerce,
to persons other than licensed importers, licensed manufacturers,
licensed dealers, or licensed collectors, any package or other container in which there is any firearm or ammunition without written notice to the carrier that such firearm or ammunition is being transported or shipped; except that any passenger who owns or legally possesses a firearm or ammunition being transported aboard any common or contract carrier for movement with the passenger in interstate or foreign commerce may deliver said firearm or ammunition into the custody of the pilot, captain, conductor or operator of such common or contract carrier for the duration of the trip without violating any of the provisions of this chapter. No common or contract carrier shall require or cause any label, tag, or other written notice to be placed on the outside of any package, luggage, or other container that such package, luggage, or other container contains a firearm.
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In other words, if you are shipping the pistol to a federally licensed entity, which you should be if its crossing state lines, then you don't have to tell the carrier anything.
Another guy put alot of this information together on his website, here:
http://www.1bad69.com/keltec/shipping.htm