The M4 can be fired in two ways, either semi-automatic (which fires one bullet when the trigger is pulled) and three-round burst (which fires three bullets very quickly when the trigger is pulled). The M4A1 can fire fully automatic instead of three-round burst. The carbine can have an M203 grenade as well as the newer M320 grenade launcher mounted on it. The M4 can be fitted with many accessories, such as night vision devices, silencers, laser pointers, telescopic sights, bipods, a shotgun, and forward hand grips.