The rocket launcher sound replacement method won't allow you to use custom sounds in pure, although you can probably lower the volume of the default sound by changing "volume" or "soundlevel" in the scattergun weapon script.

If you're using weapon scripts for custom crosshairs already, you can edit it right in there, otherwise the script can be extracted from tf2_misc_dir.vpk (it's in the scripts folder and called tf_weapon_scattergun.ctx) then decrypted with CtxConverter/vice. At that point, you can edit it like a text file (change volume or soundlevel) and then put it in tf/custom/whatever/scripts/tf_weapon_scattergun.txt and it'll override the built in one.

would i just add "sound" / "soundlevel" to that file or?

Sorry I should've looked at the game files before posting, it's actually volume and soundlevel under the Weapon_Scatter_Gun sections in scripts/game_sounds_weapons.txt, same file as the rocket launcher replacement

sick ty :D
how would i go about getting an unedited version of this file

Should be in the same location as the weapon scripts, scripts folder in tf2_misc.vpk. You can extract with gcfscape

so i've done this and changed both "soundlevel" and "volume" for "weapon_scatter_gun" but there seems to be no difference in audio
ive put the file in custom/scatter/scripts
im also using vtf crosshairs so maybe its conflicting with that file? im not sure

edit: i was changing the wrong value within game_sounds, ("scatter_gun_double" instead of "scatter_gun_single") so i got it working in the end :D
also etf2l admins said it was okay to use, as long as you dont change continuous loud noises (minigun rev, flamethrower, etc) and you dont change the volume of explosions but pistol + smg is fine (unsure about rgl / ozfort however, if ur using this then check for yourself)

here is it working with scatter + pistol + winger on half volume

edit 2: idk why but sometimes this just doesnt work in spenny dm / serveme, its very inconsistent even with preloading and ive yet to figure out why