I know weight is subjective but is there an industry standard on calling a carbine light? Is there actually a prescribed weight on a chart somewhere? Just curious that’s all.
My N4 Basic as outfitted by me weighs 7.7 pounds on my shipping scale. To me that is pretty light.
With that said, I’m currently concentrating on my current build. While I’m not looking for a featherweight set up, something less than 7 pounds would be nice.
So far I’m starting with a Tactical Innovations T15BDX lower (I wanted the integrated trigger guard) and the DD 14.5" pencil barrel w/ Vltor low pro gas block.
I personally consider the 7-7.5lb range to be about max for a “light” rifle, 8-10lbs more medium (bearing in mind that most .308/7.62 combat rifles are in this range), and anything over being “heavy” (i.e., if it’s not a precision/sniping rifle you need to lighten the load).
As our own GotM4’s Project Featherweight shows, the minimum weight you’re gonna be able to get an acceptably working AR down to is about 5.25-5.5lbs. However, you’ll note he had to take some farily extreme measures to do it.
ETA: Bear in mind I’m talking about weight of the rifle itself, largely ignoring optics, accessories, and whatnot.
Could have saved a little more than an ounce going with a standard mil-spec lower. 
I actually just bought a Noveske lower AND a Tactical Innovations T15BDX…
I have been pondering building one of them with a DD Pencil Barrel, Troy TRX Extreme rail, and a Vltor mod stock with a T1 style sight to keep it LIGHT!
Be sure to post what you end up doing!
Well… use Google and compare to some other viable options. M1 Carbine, Kalashnikov, Steyr AUG, etc…