My aging, fallible memory tells me that the Army told us our M16A1 was 7.8lbs. It was very light. (compared to the 9lb M1 Garand, it was), but can remember clearly how heavy that rifle felt on my shoulder at the end of a day of drill practice or a road march.
One thing I noticed, some time ago, look at the pictures from WWII. Other than posed photos, or in combat or movement, the butt of almost everyone's rifle is on the ground
I mention the weight of the M16A1, only as something to judge against...