Pretty sure you will find that Australia's import restrictions preceded US's export restrictions (Port Arthur preceded Nine-Eleven).
Nowadays our problem in Oz is related to some (most?) US retailers' outright refusal to export gun-related items/accessories that Australians could legally import, albeit some items may require a B709 import permit.

Ammunition components are probably a bit tougher for a private individual to import though.

I hope Bruce Bertram and Geoff McDonald are self-isolating with enthusiasm!