So there's a bug on a gun, at least grendel(haven't tried other guns) that if you use a silencer, then change from burst(perhaps full auto too) to single bullet - your shots aren't silenced anymore. Tried it multiple times with different addon combinations and it's there, a really bad bug since grendel+singleshot=godlike.

ps. Didn't find a bug forum/thread topic so I decided to create a new one.