Binko,
You shouldn't have much trouble getting a gun out of Oz and into the US. I brought two nitro (post 1898) guns from Oz into the US, one in late 2006 and one in 2008 with no problems. There are several companies willing to do this for you for a small fee. I also believe you are able to act as your own importer for one gun per year for your own use (not for resale).