I spoke about the CM16 SRL in one of my other posts and i mentioned that the gun came with a built in MOSFET. I will be going into more depth into that this post.
A MOSFET is a small board located just after the battery and before the switch and it controls electrical flow from the battery to the motor of the gun. This stops the electrical wires from burning out and it also allows you to use a higher voltage battery in the gun.
The MOSFET does not allow the gun to shoot unless the circuit is fully complete. Having a weak connection will cause arcing and that will cause carbon build up on the trigger wires inside the gun.
Battery's do not have a constant flow of power. The MOSFET regulates the battery and slows down the effects of carbon bulid up on the connections. If you do not use a MOSFET and you run high voltage batterys it is going to cause your trigger connections to arch and become sticky and this will cause the guns trigger to get stuck and potential break your gun.