Ammunition And Components of 
Ammunition
To import ammunition and components of ammunition into 
Australia, importers must first obtain written certification from the 
police firearms or weapons registry in their State or Territory, the 
Commonwealth Attorney-General’s Department, or the Minister 
for Home Affairs prior to importation. 
Ammunition for use with firearms, also known as rounds, bullets, 
and cartridges, is controlled under the Regulations. This includes 
ammunition for paintball markers, soft air (BB) pellets as well as 
ball or shot projectiles for muzzle-loading firearms.
Components of ammunition include projectiles, cartridge 
casings, whether new or spent, and primers designed or adapted 
for use in ammunition are also controlled under the Regulations 
and require permission to import prior to importation.

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AND customs

Explosives - ammunition, fireworks, igniters. In accordance with the Universal Postal Union Convention and the Australia Post's Terms and Conditions, the insertion of replica and inert explosive devices and military ordnance, including replica and inert grenades, inert shells and the like, is prohibited in all international mail. For further details please refer to Clause 62 of the Australia Post's Terms and Conditions at auspost.com.au

Buffalo Arms won't ship brass outside of America unless you use the services of an exporter/importer.  American law prohibits the exportation of brass without the right permits.  Same with scopes, bullets, and some gun parts.

I believe the only exception is old style shotgun brass for some reason.  Around here the exporter/importer adds $50 to the order price.  Tolerable if you need something that is rare and you want a fair bit of it.

Chris.

Mike when I buy something from Buffalo Arms that needs an exporter/importer I use a Canadian company ( Prophet River Importing ), they have a company in America that is an FFL and handles the export paperwork.  Buffalo Arms sends the American company my order, I send the Canadian company $50 plus shipping and a few weeks later it's at my door.

I don't know if there is a company that deals with Australia though.

Chris.