SamOlson: Heres where you are wrong!
I have posted previously of this family (friends of mine) here in SW Montana and their use of the 223 Remington Rifle they own to kill not only Mule Deer but Antelope, Whitetail Deer and a Mt. Goat.
Specific instance #1:
I was there when their teenage daughter killed a trophy 31" Mule Deer over in the Powder River country of eastern Montana!
That trophy Mule Deer Buck was HUGE!
AND... it was killed with one shot!
Broad and sweeping statements are quite often erroneous.
I suggest you get some first hand experience before you make statements like you have in regards to the 223 Remington's lethality.
Carefully placed shots through the heart/lungs of Deer sized game WILL render said creatures dead - I know!
Hold into the wind
VarmintGuy