The book "2012 Airsoft Technology Self-Paced Training Series Practical Airsoft AEG Mechbox Upgrade: M4, SR25, MP5 & G3" teaches you how to optmize your V2/V2-variant based AEG gearboxes. To achieve ultra high FPS, you need to make sure the entire mechbox mechanism is optimized in such a way that the desired FPS can be produced without sacrificing ROF and battery life. High FPS performance must be achieved with practicality in mind - you should not need to trade off power with other performance factors, and the gears should not get striped too easily. On the other hand, to achieve ultra high ROF you'll need to make sure the entire mechbox mechanism is optimized in such a way that piston movement is fast enough to produce the rate of fire desired. That means you need to use techniques to reduce the friction introduced due to fast movement, to ensure the spring can rebound fast enough after compression, and to reduce the overall workload of the gears and the motor. The primary goal of this guide is to help you improve FPS and ROF in a cost effective way. Different mechbox modification techniques are covered. Additionally, we address the issues of air tightness and battery configuration which are outside of the mechbox but are still highly relevant to the overall airsoft AEG performance. Steps for taking down the M4/G3/MP5 gearbox are also included. Both standard and EBB gearboxes are covered as well.