although there is no gunpowder, the acceleration in a railgun is quite violent and the projectile needs to contact both rails while it is being accelerated. the

although there is no gunpowder, the acceleration in a railgun is quite violent and the projectile needs to contact both rails while it is being accelerated. the smoke is probably just from the friction of the projectile against internal components. the flash could be from the same or an electrical arc (railguns use very high voltages). another possibility for the "smoke": powerful railguns often use a pressurized gas to start the process of firing. if the projectile were stationary at the time that current was applied, it might be spot welded in place.