I'm not sure of your interest in the "usual" number of shots needed. The only rule necessary is to shoot as many rounds as are necessary to stop the threat or threats that are coming after you or your loved ones. If you can do that with one shot, so be it, if you have to empty three mags, and can justify the necessity, so be it.
Originally Posted by cluznar
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well armed lamb contesting the vote."
~ Benjamin Franklin (maybe)