Iron Walls Operation - Mocheni Turret question

Does anyone know of any good ways to wipe out the defending team in the underground section of the B flag (Mocheni Turret)? I've lost the last 5 Operation games I played on Iron Walls because of that single flag. I've even tried grenade spam with Medic, Assault and Support and can't get more than two or three of the 12+ players that wedge themselves in that flag every game.