Shot a doe this weekend with my new toy, an EOTECH equipped S&W M&P 15 5.56, using DRT 79 gr frangible ammo (sent to me free by the company a couple years back during a prior debate on the same subject). Range was about 50 yards. She was quartering slightly away. Hit her mid chest on her left side, exit was through her right shoulder. Exit wound was approximately 1". For roughly 30 yards, there wasn't a drop of blood, but, after that, it was like a red carpet... I guess it took that long for her chest cavity to fill up. Found her after about another 40-50 yards.

I think the weapon and the bullet performed quite well on her. Though, she traveled a little farther after the shot than any of the deer I've shot with my .30-06, 7mm Rem Mag, 7mm-08, or .243. If I was gonna shoot a buck, I'd probably opt for one of my bigger guns, simply based on the fact that they've got more precise optics, but, based on performance on the doe, I have no doubt that the .223 would work just fine.