***The first time I shot an M-16, the only thing I noticed was the noise the spring made.***
Same here. Basic Training in 1966. We were warned that the spring hitting the back of the stock might scare us if we had never fired an M-16 before.
A few rounds and no one noticed it anymore. Now they have added more weight to the spring making less of a thump.
My initial reaction was “What the heck? Is this thing made by Mattel?”.