I'm sure others will be along to let you know for sure, but 4-6" at 100 yards (or 4-6 MOA as the cool kids say) is pretty standard for a non-free float standard AR.
Here is an article on accuracy expectations with a stock 6920 barrel. 4" with non match grade ammo is really reasonable, but that's just my opinion.
It has already been beat to death, but the question you should be asking is, what is this gun actually for? Making clover-leafs at 100 yards and HD use don't really overlap all that much.
If you want a gun that does everything fairly well, save up and get a Colt OEM 2 with FF rail and a decent LPV optic with illuminated reticle. Or get a BCM FF upper with a LPV optic. If you want an HD gun what you have will work. If you want a 1/2-1 MOA tack driver for shooting at the range, a bolt gun might be a better option.
If your primary use for your carbine is HD then worrying about 100 yard accuracy is kind of silly. There are lots and lots of options outside of ARs that are very satisfying to shoot at the range. Bolt guns. Silenced 22lr rifles/pistols. Pistol caliber carbines. Big metal handguns. Shotguns at thrown clays. Trying to make your carbine do things that are easily done by another type/style of weapon will probably end up being a)expensive and b)counter productive to your "intended" use. For example, lighter/better triggers for ARs cost a pretty penny, and may or may not be what you want to have installed in a defensive/duty carbine.
TL/dr
If you want an HD carbine, 4-6 MOA is fine. If you want something more/better than that, does it have to be an AR? Why?
Just my opinions of course.