Let me first state im not at all advocating the 22 LR as being the primo choice of defensive calibers.
However having been shot in the sternum with one I have a slightly different perspective on the issue than most .
No another person didnt shoot me thank goodness. While raccoon hunting several years ago our dogs treed one of the little corn eating bandits. Climbing up on a cliff we were almost level with the limb the critter was in and I attempted to shoot it with a colt 22 frontier scout. The gun cracked and something hit me square in the chest then began to burn like a hot steel rod stuck in my chest.
The bullet had hit a knot on the limb right below the critter and ricocheted almost straight back coming in about three inches low and left of the end of the muzzle.
After pulling open my heavy coat and shirt the bullet fell out and hit the leaves. Looking at my chest it had penetrated a heavy hunting coat, flannel shirt long underwear shirt and t shirt went thru the skin and hit my sternum. The heat of bullet cauterized the wound itself so only a drop or two of blood came out. This mind you was after being shot a good thirty yards at the critter and then glancing back losing energy im sure.
One of the two hunting partners I was with made me stand stock still until he found the bullet and asked if I wanted it. I replied that no I had had all I wanted to do with that particular bullet thank you. He kept it and wore in on a chain around his neck until he passed away saying hed never seen such a thing and probably never would again.
My point being that even with that shallow wound caused by a glancing bullet the pain was intense, in the form of burning.
Fired from a rifle or even a pistol capable of delivering 10 to 17 rounds in rapid succession it would take a very determined attacker to keep coming with each round just causing that much pain not counting the likelihood that those bullets would be going deeper than a ricochet did.
As I said im not advocating the 22 lr use as a primary defensive round. Or that some one very intent or high wouldnt make it thru a hail of the little buggers. But I also dont discount a 22 semi auto rife packing 14 rounds as secondary HD weapon either. They may not be big and loud and blow holes like coffee cups but they hurt like the dickens