I have built a lot for customer and I had one of my own. I had Custom Ar15 I built. It was great I loved it a lot. The only down fall at that time was not a lot of ammo choices but now there are a lot more.
68forums.com way more than you ever wanted to know about the 6.8. Also ammo presale notifications from silver state armory. Imagine a platform the same size and weight as a standard m4 with enough power for pig, deer, black bear elk and antelope. Yet less recoil than the 7.62 x 39. Premium hunting ammo from 17.50 to 27 a box. And you can reload it yourself for about 40 cents a shot. A great deal if your a hunter. 3/4moa out of mine for accuracy.