There is an inconsistency in the sound of triggers' reset after firing your weapon in semi-auto firemode.
When firing in fully automatic, holding down on your fire button simulates pressing the trigger - you can hear your weapon firing, and then when you let go - you can hear your trigger springing back into the default position.
When changing your firemode to semi-auto, holding down your fire button won't make your character hold the trigger after the shot is fired - you can hear it springing back in place despite the fact you're still "holding it".
It's a really tiny thing, but fixing this little inconsistency (if, of course, possible) would really help for the immersion. Devil is in the details, and every splendid detail adds up to overall greatness.
Cheers, and thanks :)