I don't know if that is a silencer or a flash hider. A good friend of mine, a sniper, in the book "Black Horse Rider" tells of picking off several NVA in a bunker during an ambush. It didn't take long for them to realize that he was a sniper and find him and concentrate fire on his position. He thought he was dead but the log he hid behind took all the hits. It is the same battle in the AHC channel movie "Rescue at Dogshead" but that movie leaves out the story of the trapped infantry. There might be a feature film coming based on that battle. Anyway a flash hider is pretty important in some circumstances.