I'm not sure about that. give me the regs.
If using USPS it has to go FFL to FFL. And they had to have filled out a Form 1508, bring that and a copy of their FFL to the Post Office so it's on file.
USPS regs here:
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12.1.2 Handguns
Handguns and other firearms capable of being concealed on the person are nonmailable unless mailed between the parties listed in 12.1.3 and 12.1.5 after the filing of an affidavit or statement required by 12.1.4 and 12.1.6, and are subject to the following:
a. Firearms meeting the definition of a handgun under 12.1.1b, and the definition of curios or relics under 27 CFR 478.11 may be mailed between curio and relic collectors only when those firearms also meet the definition of an antique firearm under 12.1.1h.
b. Firearms meeting the definition of a handgun under 12.1.1b which are certified by the curator of a municipal, state, or federal museum which exhibits firearms to be curios or relics of museum interest may be accepted for mailing without regard to 12.1.3 through 12.1.6.
c. Air guns that do not fall within the definition of firearm under 12.1.1a that are capable of being concealed on a person are mailable; but must include adult signature service under 503.9.0. Mailers must comply with all applicable state and local regulations.
d. Parts of handguns are mailable, except for handgun frames, receivers or other parts or components regulated under Chapter 44, Title 18, U.S.C.
e. Mailers are also subject to applicable restrictions by governments of a state, territory, or district.
12.1.3 Authorized Persons
Subject to 12.1.4, handguns may be mailed by a licensed manufacturer of firearms, a licensed dealer of firearms, a licensed importer of firearms, or an authorized agent of the federal government or the government of a state, territory, or district, only when addressed to a person in one of the following categories for use in the person's official duties:
a. Officers of the Army, Coast Guard, Air Force, Navy, Marine Corps, or Organized Reserve Corps.
b. Officers of the National Guard or militia of a state, territory, or district.
c. Officers of the United States or of a state, territory, or district, whose official duty is to serve warrants of arrest or commitment.
d. USPS employees authorized by the Chief Postal Inspector.
e. Officers and employees of enforcement agencies of the United States.
f. Watchmen engaged in guarding the property of the United States, a state, territory, or district.
g. Purchasing agent or other designated member of agencies employing officers and employees included in 12.1.3c. through 12.1.3e.
12.1.4 Affidavit of Addressee
Any person proposing to mail a handgun under 12.1.3 must file with the postmaster, at the time of mailing, an affidavit signed by the addressee setting forth that the addressee is qualified to receive the firearm under a particular category of 12.1.3a through 12.1.3g, and that the firearm is intended for the addressee�s official use. The affidavit must also bear a certificate stating that the firearm is for the official duty use of the addressee, signed by one of the following, as appropriate:
a. For officers of Armed Forces, by the commanding officer.
b. For officers and employees of enforcement agencies, by the head of the agency employing the addressee to perform the official duty with which the firearm is to be used.
c. For watchmen, by the chief clerk of the department, bureau, or independent branch of the government of the United States, the state, the territory, or the district by which the watchman is employed.
d. For the purchasing agent or other designated member of enforcement agencies, by the head of such agency, that the firearm is to be used by an officer or employee included in 12.1.3c through 12.1.3e, Authorized Persons.
12.1.5 Manufacturers, Dealers, and Importers
Handguns may also be mailed between licensed manufacturers of firearms, licensed dealers of firearms, and licensed importers of firearms in customary trade shipments, or for repairing or replacing parts. 12.1.6 Certificate of Manufacturers, Dealers, and Importers
A federal firearms licensee manufacturer, dealer or importer need not file the affidavit under 12.1.4, but must file with the postmaster a statement on Form 1508 signed by the mailer that he or she is a licensed manufacturer, dealer or importer of firearms. The mailer must also state that the parcels containing handguns, or parts and components of handguns under 12.1.2d, are being mailed in customary trade shipments or contain such articles for repairing or replacing parts, and that to the best of their knowledge the addressees are licensed manufacturers, dealers or importers of firearms.