I've had a 6721.
Your rifle is fine for someone wanting a HBAR DI. You have a very good Colt that would address most peoples' AR needs.
I'm not a fan of: Carbine length gas systems, HBARs, fixed front sights and DI guns. However, that's just my opinion.
ETA: if it works for you don't worry about it.
Last edited by Architect; 03/19/16 03:20 PM.