I am not sure, but my BA ticket says 23Kg for BA flights and 20Kg for my SSA flights. My trip is in August.
To avoid the SAA airlink weight/size rules (I was told no guns period) you have to get the ticket issued on the other air line so their rules apply. Example: I fly Emirates to Bulawayo on a single ticket so Emirates rules apply, even though SAA Airlink is the carrier from Jo'burg.
Steve with Travel With Guns takes care of this so you don't get your guns rejected on last leg providers.
Look into it to make sure you're good.