Thanks all. I appreciate the advice and knowledge on the subject. The whole reason for questions is to see what all I can do with an AR15. I'm pretty set on getting one in 5.56/223 for plinking, zombies and world take overs but wanted to know if I had the option to transition it to a gun I can shoot deer with as well. Seems like the 6.8SPC it a good choice. Of course it will be awhile before I even get to that point. Again thanks.