In MP, on a dedicated server, the gunfire sounds from the MX SW (arifle_MX_SW_F) are not audible if another player is firing the gun.
Player can hear themselves shooting, and if AI shoot it's audible. But if a player fires the gun, it's inaudible for the other players.
In MP, on a dedicated server, get a player to fire an MX SW, note lack of gunfire.
See video for an example: https://youtu.be/Tz6vDC059s8
The guy in front of me turns around and fires at the Strider - you see tracers but no audio.
Relevant RPT file:
(couldn't see anything relevant).