I don't plan on making a habit of shooting out that far, but would like to know that the option is there should I need/want to. I was wanting to stay with the 5.56, then changed my mind to the .308...then went looking at 6.8...then went back to my original plan of the 5.56. I have been back and fourth on which would be best. I suspect the majority of my shooting to most likely be well within the 400 yard range but would like to know that the option of reaching out is there. Thing is I have a Spikes Tactical lower already that I am building. If memory serves me the .308 will not fit the standard AR lower or am I mistaken here?
I am liking
this Stag 6.8 and here is
the 5.56 that I was originally looking at and seriously considering....
I would urge you to pass on the Stag. I had a Stag 5H, which is their 16" carbine 6.8. During the 8 months or so that I had it, I could never get it to feed reliably. This was with every kind of 6.8 ammo and magazine I could get my hands on. While I realize this does not mean every Stag 6.8 is a dog, they have had significant problems with their 6.8 rifles. For one thing, although the original and Spec II specs call for M4 feed ramps for the larger cartridges, Stag until very recently refused to use them. If you have perused the 6.8 forums, you might have seen a poll from this past winter. It showed that 43% of the Stag 6.8 owners (5H and 7H) that responded had had some sort of feed problems. Given the other alternatives in all price ranges, I can't recommend a Stag 6.8 to anyone.
If you want a high quality upper, may I suggest either Bison Armory or AR Performance. I personally have owned 2 AR Performance uppers, and that is what replaced my Stag. Harrison, who runs AR Performance (posts here as "Constructor",) is one of the definitive authorities on the 6.8, and was instrumental in the newer improved specs for the cartridge. He can build you anything from a basic M4 style 16" midlength to a long barreled Stainless target or hunting rifle. Plus he is right down the road in Pueblo West.
If you want to get into the 6.8 on a budget, stay with Palmetto State, but get one of their house-brand 18" stainless uppers. While they are currently out of stock, they have been in and out since the introduction a couple months ago. I recently picked up one of these as a second upper for my Daniels 5.56, so my kid could have a 6.8 when we go hunting hogs.
As to .308s, you remember correctly. AR styled 7.62x51/.308 rifles are built on several different, larger, non-compatible platforms. While some small parts will interchange, like handgrips, the major parts like upper and lower receivers, won't interchange with each other, or the AR15 platform.