A .22 lr is better then nothing, but not much. IMO, nothing smaller then a 9mm is suitable for self-defense, and that’s pushing it. Do not ever count on being able to place a shot in the forehead, or in between the eyes, or where ever else you think a .22 lr will stop someone, because chances are you’re not going to be able to do it. In a kill-or-be-killed situation, you will be shaking like a hound dog shitting peach seeds. You will not be able to deliver the accuracy needed to put one between someone’s eyes. What you should do is aim for center of mass, (middle of the chest) and double tap, (two shots). Then if the bad guy doesn’t stop, give him two more. You should use the largest caliber you can comfortably shoot with. If a 9mm recoil is all you can handle, then fine. But if you can safely and accurately shoot .45acp or more, then do it.