A 9mm equates to about .354 inches or about a 36 caliber.
A .22 is a good weapon, but shot placement is very important. The best advice I ever got was from a former sheriff. He told me that in a self defense situation, don’t use anything unless it has a “4” in it.
40, 44 or 45 caliber. Our self defense weapon is a Taurus Judge loaded with .410’s 000 buck and 45 long colts.
I was at a local Gander Mountain looking at a smaller 40 than the one I currently have for carrying purposes. There was a young lady working there that gave me her philosophy for defense:
If it is less than 40 caliber, empty it. If 40 or 45 - two shots center mass. if it is still moving, 2 shots to the head. If it is still moving - run, it’s demonic.
I took an instant liking to her