Alpha Parts CNC Gearbox shell for Systema PTW M4

The APARTS CNC Gearbox allows the training weapon to operate smoothly and reliably under high internal stress, while reducing the overall package dimension. This mechbox is a direct replacement for any M4/M16 Systema PTW Training Weapon, and is a high quality upgrade part to the regular PTW challenge kits. One of the most important aspects to this particular gearbox is that it'll allow the user to use ambidextrous selector switches.