Well. the .22 is one of the most deadliest calibers in the US causing the majority of fatalities.
Part of this is because it has enough power to enter the body cavities but not enough to exit. So, it just bounces around inside the cavity a bit. The end result is, it has one entry hole, but in the cavity that it entered, well there are several other little channels it made as its energy was disapated as it tried to get out.
As for a .22 with silencer, eh, simply nail the sucker in the back or side of the head, or a front or rear shot to the upper chest would do the trick. The end result scrambled brains, or the heart and lungs would have half a dozen holes in them.
In my anatomy class we actualy had a portion of such injuries, at least I think it was anatomy. Where the person was shot in the abdomen and the round came out after traveling along the femur <and devestated the femoral artery> or was it vice versa? A leg shot that traveled up the femur and into the abdominal cavity?
But, yeah, what they all said, energy, rifles and rifle calibers have more energy where as pistols and pistol calibers do not. And also velocity. Remember the design of the projectile as well. Pistol bullets tend to be run nosed allowing them to slow and disapate energy faster. Rifle bullets tend to be pointed with the tappered base <spitzer> so they by their design go faster and penetrate more.
BUT, also higher velocity rounds tend to fragment when they hit something too. Pistol rounds need to be specialy designed for that so they expand as in hollowpoints like Speer Gold Dots and Winchester Black Talons and others.