So if I can pump 3 or more shots into an intruder with my 22 pistol at point blank range is this as potent as one shot from a 9mm or 45?
22 LR, 40 gr LRN bullet 104 ft lbs of power per hit
380 95 gr FMJ bullet 155 ft lbs per hit.
38 spcl, 158 gr FMJ bullet 158 gr 200 ft lbs per hit
9MM 124 gr FMJ bullet 351 ft lbs per hit
45 ACP 230 gr FMJ bullet 365 ft lbs per hit
Additional hits with a 22 do not equate to a single hit from a single larger caliber bullet except for making more holes to bleed out of. Waiting for a bad guy to bleed out is not conducive to the welfare of his intended victim.
A 38 spcl with a good defensive round in it will beat the number I posted and would be the minimum I would feel comfortable with.