If your flying Qantas or Air NZ and booked straight through to South Africa on the same airline, then you shouldn't have a problem. My experiences with both airlines has been great and completely hassle free.
Any other airline, especially Emirates, prepare for a headache of two, or three, or four... Many airline simply won't transport firearms without special circumstances and heaps of advance notice.
Australia can be a problem if you're not familiar with the local system and procedures. The Australian Border Security team leader ( whose team specifically deals with firearms and alike) at Sydney International airport is very helpful and professional, and a great lady to deal with.
Feel free to PM me, also happy to chat on the phone.
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