Military Standard of a 5-inch group with iron sights at 100 yards
5 MOA with Iron sights using military spec M855.
I would actually call that pretty respectable. Shooting that with a magnified optic using match grade ammo, wouldn't be very good.
The spec for the M-14 was 8 MOA with M80 Ball which doesn't have a seperate steel penetrator that can be assembled out of the centerline of the bullet and cause wobble.
It is true however, if you want a super accurate gun, Colt 6920 ISN'T the way to go. (No combat rifle is)
Something with a high quality stainless or standard chrome-moly free float barrel with give much better accuracy and if you are chiefly worried about accuracy and not so much reliability, a nice tight .223 Remington chamber and staying with match rounds will help alot.
Thanks for the link.