After reading several threads regarding shooting whitetails with 223, I decided to see for myself. I went out last week with my AR with the intention of culling a couple of does. I shot two small does (about 75 lbs each). Ammunition was 55 grain soft point. Both deer were shot broadside at about 100 yds. The first one apparently hit the shoulder bone, mushroomed, and caused a great deal of internal damage. No exit wound, DRT instantly. The second one was a double lung shot with a small exit wound on the opposite side. This deer ran about 10 yds, collapsed, and died about 30 seconds later. These were very small deer, but I am confidant with proper shot placement this is an effective round. I imagine with a 68 grain bullet the results would be even better. My family enjoyed the backstraps on Christmas day and the rest is in the freezer.