There's no such thing as knockdown power? Hmmm.......that's probably not far from true if you're talking about the 22 cals. on deer sized game. Bullets are too lightly constructed to deal with deer anatomy for the shots I take.

We all know if you hit a deer in the head or spine with just about any rifle, it will drop. In hunting situations, I don't take head or spine shots. For shots that are basically broadside or somewhat quartering away, I always aim at a point where I can visualize my bullet striking the OFFSIDE shoulder. For a quarterting towards shot, I basically center the body between the shoulders. It has worked well for me. I shoot either a 308, .30/06, .54 cal muzzleloader, 12 ga slug or 45/70 at deer.

I do rely on good penetration, and by far prefer complete penetration over one entry wound. I take shots that would not be adviseable with a 22 cal rifle.

That said, I know that a 22 cal in capable hands will work, as long as the correct shots are taken. There is less margin for error though, and hunting situations can introduce lots of sources for error, like unseen twigs, wind, the game moving at the instant you fire, not to mention all the human factors like elevated heart rate, jitters, and the like.

If someone asked me what caliber of rifle to buy for deer hunting, I would start at 243 Win or 260 Rem, and go up from there based on the particular application. If varmints are part of the equation, then maybe a 250-3000 would be ok.