A .22 rifle round apparently will penetrate their armor and kill them but not immediately. You still get the show of it pinballing off of whatever is around as it jumps higher than expected and runs with surprising speed. Ask me how I know.

On the bright side I didn't have to clean up what I have read is a very smelly mess. That said, I think I'll go with the AR15 next time and know for sure.
SA-TX