ok then you are right in getting a mosfet to run a Lipo battery but you could the gearbox to cycle without it !
but enyway get your mosfet but be aware that some are merely burst fire gimmics so reserch on youtube what otheres are using
i think as long as the owner of a RIF is not a d**k then its ok ,but on the othere hand we need to show we eat rules and regulations for breakfast and show that we are doing the hole airsoft thing by the book instead of being looked down on because we love guns