First and foremost, check your state regs, most states either have a minimum power factor or a minimum caliber that prohibit the .223rem from being used on deer...I won't say it isn't done, but it's not legal in most states, before you unknowingly go poaching, check the books.

As for my opinion, the .223 works for deer, I've used a .22-250 on deer in TX to fine results. Granted the .22-250 tends to handle heavier bullets a little better than the .223 (depends on your gun honestly), but the results were such that I never felt undergunned. I ended up using the .22-250 to start with after getting a bizarre chance to take a hunt all expenses paid while varmint hunting in north texas one year, it was the only rifle I had with me, so I used it, and it worked for two deer, a 8pt buck and a good sized doe.

My aunt that I was staying with at the time ONLY uses a .223 for deer, she's taken 9 or 10 in the last 4yrs since she started hunting.

Most people think the 22cal centerfires are all under powered because they've never used them on deer, maybe a few people have heard bad experiences, but they've never taken one out day in and day out for years and actually seen what it does. I still won't say that I'm "experienced" at hunting with a .22-250, but I'm pretty commonly found hunting with "under powered" cartridges, and I've yet to have one "get away" from a "weak" cartridge, while my .30-06 in fact HAS had one get away after a sure hit (broadside, she rolled over, layed a second, jumped up and RAN, no blood trail, 4people in my party looking for over an hour!)

I'll also say this before I close, I would never recommend anyone buy a .223 as their starter deer rifle, because it is NOT a beginners deer rifle, nor should it be your ONLY deer rifle, however, if you're an avid varminter and you've got one, or you're simply an avid hunter who's wants to try out something different than the ol' 06, then it's a viable choice. I give the opinion I give on this board because most of the people here aren't your average, "yeah I've got a hunting rifle" hunters, and most of us can understand the difference between going afield with a gun to shoot a deer and going deer hunting.

For example, I have an uncle who's often known for claiming he's been hunting out of the same 2 boxes of .30-30 rounds he bought when he bought his rifle for the last 20yrs. Although it's admirable that he makes good use of his shots, taking less than 40shots in 20yrs isn't something to brag about!!! He's not one I'd trust to take a .223 hunting.