Greetings,
I have had a Carbon15 Ultralight for a while now.
It has FA and DC on it.
Still have parts of it....it was SO BAD, we nicknamed it The BushNasty.
Problems I have had so far with MY Carbon 15:
The rail became loose and we had to remove it and reinstall it with golf club shafting epoxy and fill what was left of the screw hole threads with epoxy and push the screw in. Let it sit for 24 hours and that was fixed....mostly - strike 1!
Next up, the barrel nut threads are bigger, not standard and no "AR Standard" barrel nut or float tube fore grip will fit - strike 2!
As for accuracy, 4 to 6 inch groups are not rifle accuracy, hell, it's not even shotgun buckshot accuracy until you shoot 9 times - strike 3!
On the plus side:
It was light!
The steel mags work nice.
It has an excellent trigger job from the factory.
I'm still using the BCG, charge handle and lower parts I removed from the C15 - EVERYTHING else was replaced.
It's now a 300 Blackout that drives tacks and slays hogs!
Good news for Bushmaster fan-boys (like myself - I always wanted a Bushy) is the original owner of Bushmaster has reformed and rehired most of the original Bushmaster staff and has started Windham Weaponry in the original Bushmaster building in Maine AND offers lifetime warranty on their guns!
Windham WeaponryI'll never buy another factory AR unless it's a LaRue.
Primarily because I like to build them the way I want now.
I am on fire!!!! 
