Sure you can shoot a deer with a 223 cal bullet and if everything goes right it will die. Ok, it will reliably kill a Labrador sized white tail. They are very accurate weapons, and with the right bullet it is adequate for small deer, but it doesn't really have tremendous energy, leaves a very small wound channel, which means that this deer will bleed slowly and leave a poor trail to track if not an instant kill. I have no problem with it within its limitations. I believe that all hunters should have ethics concerning their quarry. If you have the right shot, the right shooting experience, the right bullet, the right conditions , you see what I'm getting at here, too many ifs. I'm not saying don't, but I am saying you better get it right everytime or else you're not an ethical hunter, I have a 223 rifle, but here in Montana, year before last, while there are no restrictions on rifle caliber, there were 6 hunters attacked by Grizzly bears that beat them to their kill, if you were carrying a 22-250 you would be bearfood. I hunt mule deer with a 300WBY and with the right bullet it will not blow them half. I'm not sure that I could ethically hunt deer with a 22.