Most of that "sound" you objected to can be cured with judicious application of some Tetra grease....and the targets the AR produces can make that "rusty screen door" a "Happy Sound" if you give it time.

FWIW, I'm an "Old Comp Dog", so I've got both a .308 Garand and an M14icon. Both have virtues and limitations just like any rifle....I like'um both!