She fired, missed, and the guy sat down and waited for police. He's saying a starter pistol would have had the same affect. The noise and the sight of the gun is what stopped him, the caliber was irrelevant in this instance.
Funny how a miss with any caliber proves anything about its effectiveness.
All that said, my grandmother used a .22 revolver to defend herself. She didn't have to fire a shot, the fellow knew she wasn't bluffing when she told him if his foot hit the top step he was dead. What does that say about the .22? Nothing. What does that, and this article, say about mindset and refusing to be a victim? Plenty.
Well, she wasn't using a starter pistol, or a nerf gun and a firecracker. Neither of which, by the way, sound like an actual gun shot. There is no way of knowing that a starter pistol would've had the same effect, and I'm betting that it wouldn't have.
Props to your grandmother!