i have stock tm gears,CA piston,sys. silent head set,a bearing spring guide and a 110 spring in my m16 after 3-4 months and 50,000 (at least) bb's shot using a 9.6v the only thing i need to replace is the gear on the motor (I opened it up today to make sure everything was copesetic). its teeth got sharp. the most important thing is that you get metal bushings and shim the gears right