The front of a pig skull is very thick...
Lung shots are ineffective in general...
The CCI velocitors can penetrate 15 inches in ballistics medium from a Ruger SR22 pistol. From the tests people have posted online.
A 22 is not the best defensive round, but if it hits something important it will do the job. More rounds doesn't really mean much, though it will cause more pain as the count rises, which may stop a threat. It also increases your chances of hitting something important, but this is true of all calibers.
As was said, it beats having nothing at all, but there are better round choices, and they offer distinct advantages.