Rapidfire works with all guns, but there isn't much benifit to using it unless the gun is semi-auto. Snipermode works for all scoped guns (not acog, but thermal or sniperscope), and you must select the proper mode for fast reloads, they are categorized by gun. I asume you are talking about COD, because fast reload and snipermode are designed for COD, but there are many different rapidfire settings.