In technical terms, the recoil caused by a gun exactly balances the forward momentum of the projectile and exhaust gasses (ejecta), according to Newton’s third law. Because rail guns do not use a rearward propellant and all the momentum is transfered between the rails (which surround the ‘barrel’)and the projectile the transfer of that momentum to bring the equation back to zero does not constitute recoil in the classic sense.
Does the raft move?