The Forgotten Weapons video says that probably less than 100 of these were ever produced, and the production line never managed to make one that worked properly. This seems like an important detail which is missing entirely from the Wikipedia article. (There used to be a paragraph mentioning the small production run, but it got lost in this edit[1] in 2021.)

[1] https://en.wikipedia.org/w/index.php?title=Mamba_Pistol&diff...

And some more background https://en.wikipedia.org/wiki/Rhodesian_Bush_War