Worthy? NO, possible? Yes, that's why I have such things, better than a sharp stick in the eye, but a stick can reach the good stuff, if it's a good stick. I have these cartridges, and in my .22's they do shoot pretty well, but I have seen other pistols, Keyhole these rounds, and it looks impressive on paper, but on flesh, probably would not penetrate. Rimfires to the head are iffy, especially from the front, from the back of the head, in the Medulla AKA, GANGLAND STYLE, is a different but not guaranteed result, but more predictable, they used Icepicks too in the same spot, I don't want to defend that shot in court, but it could be defenseable. If it is what you have, then the discussion is over, use what you have to it's best advantage, and hope for the best. Remember Reagan was shot under the armpit with a .22rf, and did not know it for a while, granted it was not one of these, but I don't think the result would have been much different, maybe would have gotten his attention sooner? The .22rf is a killer, because it makes lots of small holes for surgeons to find, before you bleed out, but you probably drove yourself to the emergency room, I would use solids over HP's for penetration, but that is abstract, in a small bullet such as a .22rf. That said, here is my stealth holster, shirt pocket carry.

Now my well worn Tomcat .32 and my NAA Guardian.

I'll keep my 9mm, revolver in the front pocket, but the little gun has its small place, I won't be loading my S&W 41 with the Aquila rounds on my hip, in favor of my Para .45's or my Kahr k40.