Matt,
I agree with you about the attitude to firearms in NSW - their registry would have to be THE most difficult to get along with in Australia! A (long) while ago, I had the task of moving a couple of Commonwealth-owned semi-autos from Canberra to a Commonwealth facility in Vic and back again, and we were going to move them in a Comm Car. Checked with Victoria: no problem. Checked with NSW - where the offending firearms would be at most 4 hours within the state each way - and was told ONLY with a Ministerial approval which might take months to approve!
Answer: moved them by commercial courier at Commonwealth expense, which was legal in NSW.
So when I saw you were making scale replicas, it crossed my mind that you were dealing with the most draconian state of the Commonwealth when it comes to firearms, and it might not be worth the risk. Glad (for your sake) you have come to the same conclusion.
Mike