I love playing me some SiN, but a bug that seems to occur for me during play throughs is when you eventually get a silencer to you machine gun or pistol, I know its a minor complaint but I really dislike the generic sound effect it makes and the fact I have no idea how to remove it, is quite annoying It kind of kills some of the mood for me so id appreciate any help on this subject.
so yeah how do you remove the attachment?

bump this. I'm having the same problem. Pressing the use weapon key doesn't do anything. I know that key is stil work cause it work on other weapon with 2nd fire mode. Once you get it on you can't get it off.

One workaround for that, is replacing the SFX file for that silenced gunshot with my own. Since I've always loved the silenced Falcon pistol SFX from Perfect Dark, I just use that.
Just find some playthrough of perfect dark somewhere, download the video, or audio of that video, crop it so it's only the silenced shot and rename it to "silshot.wav", which for me, is located in "C:\GOG Games\Sin Gold\base\pak0\sound\weapons\magnum"
I do the same thing with the shotgun sound, since it feels incredibly weak compared to perfect dark's shotgun.