Every bit of bad Gun Lore is based in a sliver of truth.
This one just popped in my Facebook feed:
From my research on mass killings, I have found out that indeed, one if not the most common caliber used in taking lives is the old noble .22 Long Rifle. But for the love of JMB, I have no idea where the bouncing around crap came from but I do remember reading about it in some mobster-related stuff when I was a kid.
The truth is much simpler: .22LR is the most popular, most common and must abundant caliber in the history of the world. Grok says that anywhere from 200 to 400 billion rounds of the cartridge have been manufactured since its introduction in 1887 and that means more people felled by this particular caliber just because of massive distribution not a particular Speedy Gonzales behavior of the round inside the body.
Just to be sure, my .22 is in WMR.
I think (without doing further research that would just make me want to pull my hair out) that the "bouncing" mythos comes from stories of assassins using revolvers in contact with the victims head. If the projectile makes it inside the skull, it is highly likely to bounce off the other side. You already touched on the other salient points. 🙂