I realize this is a really old post but I wanted to throw in my two cents, for what they're worth. I use a .222 for deer hunting and have NEVER lost an animal. In fact, all the deer I've shot with it have dropped right in their tracks. Using the .222 is something that should be carefully considered though. Among the considerations are bullet weights used(My personal favorite is the 55 grain), also bullet placement should be paramount to ensure a quick and humane kill, but shouldn't this be our goal as hunters no matter what caliber we use? I use the .222 because I like the light recoil because I am not a large framed person and can't handle the recoil of the bigger guns. Another consideration to take into account when using the .222 is the distance of the shot. If you're into the "I killed this buck uphill at 900 yards over a mountain in a 70 mph wind." kind of shots, the .222 may not be for you, but if you are willing to let the animal get reasonably close, 150 yards or less, and wait until it offers a reasonable shot angle, I see no reason why the .222 isn't a lethal whitetail killer.

my knowledge on it is that the .22 is a small cartridge with little gun powder for small game, squirrel birds etc. the .222 seems to be a stepped up .22 with same caliber but with way more powder and maybe a little bigger bullet. i have a .223 and i think its a little bigger than the .223 but they are both small rounds with around 50 grain bullets