Self defence gun
The main question here is "self defense gun;" before the police went to semi autos, they carried the 38 caliber. Anything smaller than a 38 will increase the assailant's chances of surviving his wound. If you're intention is to only wound your attacker, and he'll hopefully turn around and flee, then a 22, 25, or 380 will do that job. But if your attacker decides to press his attack and kill you before he dies from excessive bleeding, then you better make your 2nd shot a head shot, assuming you hadn't emptied all your rounds in his torso. When Reagan was shot by John Hinckley, it was a 22, and Reagan walked into the emergency room on his own.