I bought an Armalite AR-10 in .308 a long while back. Really nice gun. But I bought an upper chambered for .243 for it afterwards. The .243 is such a tack driver that I sold off that .308 upper and never looked back.
If you want a REALLY eye opener of an AR-15, try one chambered for the .50 Beowulf round. Now that one is really something.
