I wouldn't have any problems using my .223 for deer. I know the limits of both myself and my weapon. For me, it is enough for deer. Although if given the option, I would prefer to have my 25-06. But my general carry gun is the .223, so often times it is the gun I have when I run across deer.

For someone that does not have a lot of experience with a firearm, a .223 is not the correct choice for deer. People on here have asked before about their kids using them. Smaller margin of error and inexperienced shooters don't mix.