It Is A Breeze.
Referring to this Shootout: http://shoutout.wix.com/so/4LoqCUBJ#/main
You are met at arrival by an expert courier who takes you to the SA Police Firearms office. You fill out a form with the rifle Make, Model and Calibre and this is entered into the SA Firearms Register. You are issued a temporary licence to carry, transport and use the gun for your duration in South Africa. It happens all the time, every day.
On return, the same person again accompanies you to assist with the rifle's exit through customs.