I think its server sided. Mmmm i heard a debate once that the .rez files are all client sided because the server couldnt hold all of that data. But everyone knows that damage is server sided when exchanging models. Only ROF and portability have shown to change (besides the significant blast range change of the LAW to spy rocket launcher) However you can mod the sound of the guns i think. You can interchange the sounds for sure and we have seen custom accolade sounds.