At about 0:57 in the video posted by metric_taper, the auto sear is described as being a "LEGO-sized device". That's a new one.

Shortly after that, they say that it makes the weapon "capable of firing 20 rounds in a second", while showing someone using a pistol equipped with it firing 10 rounds in about a second. Still pretty fast, but apparently only fairly accurate at a distance of about 45 LEGOs.