Personally I would NEVER carry a.22 rimfire for self defense, unless that was the ONLY gun I had! A .22 is better than nothing, I suppose. That said, if I was restricted to carrying only a .22 I would carry Velocitor 40 grain ammo in it. It is about the hottest .22 rimfire load at a true 40 grain weight that I know of. Regardless of brand or style, eventually there will be a failure to fire with rimfire ammo, and I don't like that concept. To me carry ammo should have a center fire primer, but that is just my opinion.
Chief38