We're seeing more brushless motor for AEG use and Krampus Airsoft takes a a look at one from Warhead Industries... "The constant contact of the brushes with the power terminals of a brushed motor is necessary for it to maintain its rotation. However, the friction that this creates means that a huge portion of the energy generated by the rotational motion is wasted as heat. Generally, the efficiency of brushed motors is limited within the range of 75% to 80%.