An Australian young ladyfriend of mine describes it as akin tio the sound that an aluminum screen door makes when pulled shut by the door spring. I wish she hadn't told me that; her description remains with me every time I fire an M16 or AR15 and I hear that noise of the spring and buffer inside the buttstock.
Though the FAL, BAR and Browning Auto-Five shotguns similarly house their recoil mechanisms inside their buttstocks, they at least all project a feeling of bobustness in their innards, no more fragile than a steam locomotive's. That can't quite be said for Eugine Stoner's aluminum and plastic brainchild, but wooden buttstocks and steel lower receivers are available for the Armalite rifle. I doubt if it'd change the perception, though.
There is, however, another alternative....
-archy-/-