The CM16 SRS is a new gun from G&Gs Combat Machine line. This gun features external and electrical improvements over the standard combat machines. The SRS has a tough, glass fiber body and an aluminum, KeyMod rail system. Internally the gun features an electronic trigger switch and mosfet (the mosfet is stowed away in the buffer tube). this gives the gun quick trigger response and a selectable full auto/3 round burst setting. To turn on 3 round burst mode (3 round burst will replace full auto in that selector position), simply place the selector switch in semi auto and hold the trigger down for 10 seconds. The gun will fire when you first pull the trigger, so please make sure to clear the gun first and point in a safe direction. To switch back, you can hold the trigger down in semi auto for 10 seconds again, or you can unplug the battery for a few seconds to reset the mosfet.