i agree with dan, as there are a lot better alternatives to a rimfire, but in a bad situation could be better than a stick. a rimfire will and can kill a person is shot placement is observed, but in a highly stressful, SD situation, shot placement could go out the door and hitting someone with a rimfire cartridge in a non-vital area could have results that are hazardous to your well being. if looking for a back-up pistol, i would give serious thought to the 380, or a small 38 revelver. i have heard of people who have carried a 22 mag. revolver or derringer type pistol for a back-up, but it's not something i would recommend personally. for me the 380, or the small 38 would be the smallest caliber i would use.