Damage not matching info stats

Was messing around in firing range and noticed that the M417A2 is hitting for only 27 damage on the 10meter target despite the stats pg saying it should be hitting for 33 damage. I noticed same issue with the SOR-300SC hitting only 25 damage while stats pg shows 33. Found simliar issue with the following weapons SCW-10, RPKM, and SVK-86.