I hear a lot of complaints about multiplayer sounds in these forums. I agree, they do sound weak, however they are just placeholder sounds, not actual sounds. Here’s my proof.
Compare the sounds of the BR between both videos. The Multiplayer gameplay sounds weak, and silenced. Campaign sounds tough, powerful, and deep. Why would they include two different sounds for Campaign and Multiplayer? It would be dumb! Plus all Multiplayer guns sound practically the same, which leads me to believe that these sounds are just placeholders for a demo, while the Campaign sounds will be included in Multiplayer for the final, production copies.
Also the explanation for campaign not including placeholders would be that it is finished. Frankie said a while back that it was complete, and wrapped up in a neat little bow for our entertainment. Multiplayer is still being worked on, so they aren’t including any real sounds as of yet.