yeah, if everything is right and good shot placement is used, a 223 will kill a deer. however, it leaves a WHOLE LOT less room for error than a bigger cal. I'd go 243 on up. Also, for the range, check a ballistics table or program and see the range that it still carries more than 1000-1100 ftlb of energy. This is widely considered the minimum needed to kill a deer. BUT WHY USE THE MINIMUM?