I just got my Scar 16S and when I pull back on the charging handle I can hear the spring scraping/squeaking (sounds like one of those shopping cart wheels that squeak) on the guide rod. After dis-assembly, I tried it with just the spring and I can reproduce the sound from it. I looked and have not seen any rust. After running some M-Pro 7 oil on the spring and trying it again a few times, the sound persists. On videos I've seen online I don't hear this sound, so I wanted to know if this was normal, and if not is this something I can have FN replace.
A few pictures:
Video clip of the charging and sound:
EDIT: Based on feedback from other members. This seems to be normal for the Scar.
I listened to your clip and then worked mine slowly like you were doing. It sounds about the same to my untrained ears. I really never noticed anything before. Of course unless sparks and chunks are flying, I'm fairly oblivious.