So let me first off note that I love this mod. I've been using it for quite a while when I play Factorio with mods. That said, is there any way to turn down the volume of the HMG? It is painfully loud to me compared to the volume of everything else.

Yes, provided you're not playing multiplayer, as it requires modifying a text file, which would cause a desync in multiplayer.

You need to extract the zipped mod (mods are in C:\Users\<user_name>\AppData\Roaming\Factorio\mods), it's named "scattergun_turret_7.3.0.zip" Then go to folder "scattergun_turret_7.3.0" -> prototypes" -> "entities" and open "w93-hmg-turret.lua". CTRL + F, search for "volume". There should be 2 instances of the following code:

    sound = 
    {
        {
            filename = "__scattergun_turret__/sound/hmg-turret-fire.ogg",
            volume = 0.35
        }
    }

Adjust the volume parameter as you see fit, value should be between 0 and 1. Once you're done, zip the mod back up.

Thank you very much.