The 223 WILL kill Elk or bear. The problem as I see it is: The margin for error with those smaller chamberings is so slight, that you can be in trouble in a millisecond. The wound channel is quite small, regardless of the bullet used. I do not subscribe to the theory that one needs a magnum to kill big game either. If you like to use one, fine, just don't give me a steely gaze and tell me that I must have one to shoot moose, Elk, bears or whatever. My idea of a practical size rifle for all North American Big game is in the 6.5x55-30-06 area. Proper bullets in most chamberings for these bullet diameters are effective and leave a bit of margin for a slight miscue. I have shot a lot of Elk, and I do not like 6mms for these big cervids. Some 25's work OK in the hands of a skilled hunter, but it's at around 6.5mm where the comfort zone starts, for ME at least. I have shot elk with the 264 Win Mag, and moose with the 6.5x55, using the 140 Partition, and they worked fine, but I didn't take any "hope" shots either. I really like the 7x57, loaded with 160 Partitions for the bigger members of the deer family, but limit shots to 300 yards or less with this one. Having taken about a dozen moose/elk with the 7x57, I have a lot of confidence in it.
If someone elects to use the 223 to shoot big game of any type, he must load with a "Game" bullet, (Partition or TSX) and be very careful to put that diminuitive
bullet exactly where it will do the deed. Personally, I will opt for a bigger gun. JMHO, Eagleye.