Is the AAC blackout non mount flash hider long enough to bring a 14.5 barrel to 16?

AAC advertises its length (5.56 version) to be 2.125" so... it's a close one, but add a washer and you'll likely be ok. My guess is your threaded portion is .500" or .650". If you have your barrel in hand you can do the math, the only variable is how much overlap you'll have but that's up to the barrel, and any washers you use.

I've been thinking of the 14.5" route with a pinned on 51tooth mount for my self. Getting two inches shorter sounds Like a nice compromise rather than going pistol or SBR length for 5.56.

If it is 2.125" long it will bring a 14.5" barrel up to 16".