It's done, and I have seen it done, w/ bamaboy and a Mini-Mauser and a 6x Leupold. Federal Tactical (read bonded) 62 gr slug the first time and a Fed bonded 55 the second.
Both deer went no further than deer have gone shot w/ heavier calibers and were every bit as dead. Both were hit properly (lungs) under very controlled settings, me coaching, rifle on a support, ideal angles, much practice prior.
First deer got a pass through and easy trail, about 75 yds.
Second deer we got absolutley no blood trail, (no exit either) though the deer went only 50 yds or so, it got into some VERY thick cover and the followup was interesting.
Proper bullets, proper placement, and ideal conditions, and the .223 can take deer. We moved to a bigger caliber the third year and the .223 is for practice and varmints now.