How good is the VFC Avalon gearbox stock? If I did not upgrade it, would it be a solid platform to use? I do know that they are very upgradable, but if you were to leave it stock, would it be an alright all around gun that will work? Not looking for a crazy rate of fire, no extremely high fps, no crazy trigger response. Just a good low stress build. Asking because I plan on building an M4a1 as a backup rifle that I can always count on, so the whole gun would ideally fire about 15 rps at about 380 fps.