Ammo, powder and primers as well as primed brass are not mailable through the USPS, they must be shipped UPS or Fedex ground, all but ammo
(and primed brass, I think) are subject to hazmat fees and shipping regs, from a previous thread on another forum a hazmat account may be required for UPS hazmat shipments.
http://www.ups.com/using/services/accs/hazmat/hzm_home.htmlTim
http://pe.usps.com/text/pub52/welcome.htm 341.21 Nonmailable Explosives
Nonmailable explosives found in the mailstream must be immediately reported in accordance with POM 139.117.
Nonmailable explosives include, but are not limited to, the following:
1. Common Fireworks. Fireworks are classified as Division 1.1, 1.2, 1.3, or 1.4 explosives depending on the degree of hazard. Fireworks include roman candles, skyrockets, helicopter–type rockets, cylindrical and cone fountains, pyrotechnic wheels, illuminating torches, firecrackers, salutes, and combinations of items that are designed to produce any of the aforementioned types of effects. All types of fireworks are prohibited from mailing.
2. Fuses. Fuses are classified as Division 1.3 or 1.4 explosives depending on the degree of hazard. All types of fuses (except safety fuses as permitted under 341.22) are prohibited from mailing.
3. Small Arms Ammunition. Ammunition is classified as a Division 1.1, 1.2, 1.3, or 1.4 explosive, depending on the degree of hazard. Ammunition that is regulated as a Class 1 explosive and designed to be fired from a pistol, revolver, rifle, or shotgun, as well as associated primers and blank cartridges (including those designed for tools) and propellant powder for use in any firearm, is prohibited from mailing.