ORIGINAL: Underclocked
The postmaster is WRONG! The USPS WILL ship Firearms gun parts (except for actions)and complete muzzleloaders - no problem.
USPSwill ship complete firearms including actions only (minus handguns)to an FFL. They have a big postal book that shows what they can and can't ship. For the firearms section it refers you to the BATF. I'm thinking that for a postmaster to refuse something that can be shipped legally is discrimination.