Yes, but SA caselaw supports a verdict of CH when a claim to PPD fails. (Apart from Oliveira).
I think that is not surprising as genuine PPD cases will frequently arise out of negligence.
As a matter of logic, I still think that OP can legitimately say that he didn't intend to kill anyone unlawfully. He can also say that his intention was not to kill but that he panicked and fired without thinking because he thought he was under attack.
I think with the right facts, you could have a cascading set of non contradictory defences
E.g. You hear an intruder. As you grab your gun, your wife jumps out from behind a door in the dark and shouts boo! You shoot once.
Defences to murder
1. Involuntary action
2. Lack of intent
3. PPD
The problem in practice is that legal foresight is not only that split second.
When OP decides to keep a gun for self defence at that point he make the decision that he will defend by shooting rather than some other method.
When he points a gun at an intruder, and many seconds go by - obviously that is an intentional decision to give himself the opportunity to defend himself by shooting.
He clearly foresees that and understands what happens when you shoot someone.
You can't then isolate a split second and say "the thought never crossed my mind"
Why point a gun at someone unless you are considering use of lethal force?
Just because you have not made a final decision yet, does not rule out foresight.