RE: 7.62x39mm for deer
almost any round will take a deer if the shot is placed right. but you might want someting that shoot decent groups. cause not always will your shot hit where you want it to go. brush twigs etc.
in the new hunt america issue. someone asked the same question and the reply was that it was less powerfull than the 30-30win but decent up close. if you use a soft point.