Since I just got a scale that goes beyond 5 pounds, I checked the total weight -- 5.8lbs. Out of curiosity, I weighed a basic AR15A2 and it weighed exactly the same. Hmmm...weight advantage goes to SU16. AR15 has a slightly heavier barrel and might have an advantage in sustained fire...or does it. AR forend traps some of the heat in, while aluminum rail of the modified SU acts as a heat sink and a radiator. Will test fire both and find out which works better.