Northern Whitetail Deer easily go over the 150lb. mark, some Bucks 220lb. I've shot Deer with .223, (once) 7.62X39MM. .30/06, and 7MM Magnum. The .223 just does not carry the punch needed to humanely take the larger Whitetails. Sure, it will kill, but you may track one for miles despite a good hit. The 7.62X39MM SP round has proven adequate up to 150 yards or so beyond that is iffy. The .30/06 will always be my preference. I've shot a couple dozen Whitetails with the 180 Grain Remington SP and the farthest one ran was 80 yards. The 7MM Magnum is very good, but seems to tear up more meat.