The whitetail deer when have down in the south is smaller than the ones y'all have up north. They dont have to contend with the cold and dont have the extra weight. The coldest it may get down here on average is the low 30s with the occasional snow fall. I would prefer to use something bigger than the 5.56/.223 round, but it will work for the ones down here. I only have a rifle that will fire that round, but could easily convert my rifle to the 6.8 (.270) by changing out the upper receiver, but will have to live with what I have until I get the funds to purchase something like that. There have been many strides for that round. I will not hunt with anything that is not designed and tested specifically for deer. If they can get a 62 grain .223 to take down a deer, I am sure a 75 grain 5.56 could do it. Just my thoughts about it. Shot placement is the key for any round IMHO.