The 22 isn't optimal at all but it WILL do the job in one shot if its really needed I have a friend serving life in prison that will attest to that.
Well, gee, you can get this sort of result with a bb gun, too. BB guns certainly can be lethal, but that doesn't make them great for self defense.
Heck, even a fork can be lethal, but I don't see too many folks talking about it as a primary self defense tool.
"If you look through your scope and see your shoe, aim higher."
-- said to me by my 11 year old daughter before going out for hogs 8/13/2011