If there isn't a flash suppressor to bridge that gap, it would be classified as a SBR. I purchased a 14.5" Noveske Carbone (Thunder Ranch) recently.
I have Eotechs (3) but I also have an Aimpoint T1. The Aimpoint has great battery life and can be kept on.
Whatever, you choose, make sure it's chambered for 5.56mm/.223. Have fun.