- "Fire forward Railguns at the lead ship."
- —Paul Emerson
- "That is a big gun."
- —Eli Wallace
Railguns are high-velocity projectile weapons which use electromagnetic fields to propel a solid metal slug at a velocity of mach 5 over a distance of 250 miles. A standard magazine carries ten thousand rounds. This impressive ammunition capacity was the result of an upgrade deemed necessary after the Prometheus used up nearly all of its ammunition in a relatively small engagement. Lt. Matthew Scott stated that they fire at a rate of 500 rounds per minute. (SGU: "Air, Part 1")
They have become standard on F-302 fighter-interceptors, the Prometheus, and all Daedalus-class vessels for ship-to-ship combat. They are mainly used as point defense weapons, as larger capital ships, particularly shielded ones, are much more resistant to them.
A railgun can easily shoot down fighters such as Wraith Darts and Death Gliders in a few shots. Larger or shielded vessels, such as Ori warships, Goa'uld Ha'taks or Wraith Hive ships, are virtually immune as long as they are expecting the attack. During the Battle of Asuras, an opening salvo of Railguns proved powerful enough to cause severe damage to an Asuran-built Aurora-class battleship, in tandem with several Wraith vessels bombarding the vessel. However, the ship likely had its shields down at the time as it wasn't expecting the attack, since the weapon by its very nature is more effective against armor than shielding.
In general, Railguns have been shown to be insufficient in defending any target by themselves. Railguns installed in Atlantis during the siege were only successful in holding off large waves of Darts when supplemented with dozens of Drone weapons, and they only moderately succeeded in protecting Icarus base when it came under attack, though at both times, they were human-controlled. Despite advantages of surprise and superior shielding technology, the Railguns on the Daedalus repeatedly proved insufficient to penetrate the organic armour on the larger Wraith ships, like the Hive ships and cruisers, and only prove useful in situations where ships with powerful shields, and thus little need for armor, were caught with them deactivated, or when they are used against smaller ships, like Darts or Gliders.
Recently, Asgard plasma beam weapons have replaced Railguns as the primary armament on Daedalus-class ships, and Railguns seem to be used as a point defense system for small fighters, a much more suitable task given fighters rarely posses shields. (SG1: "Prometheus Unbound", "Off the Grid", "Ethon", "Camelot", ATL: "The Siege, Part 3", "Aurora", "The Hive", "Be All My Sins Remember'd", "The Daedalus Variations", SGU: "Air, Part 1")
Behind the scenesEdit
In reality, the technology exists to build Railguns; however, it is difficult to obtain sufficient power for them to be effective and to get the barrel of the gun in question to withstand the extreme temperatures and speeds of the projectile, wearing out the barrel with only a few uses. Presumably, the fictional explanation for the ability to make operational Railguns would be the invention of Naquadah generators and the discovery of more durable materials, such as Trinium. In Stargate, the apparent Gatling gun-style configuration may help to keep the barrel from overheating. In addition, real-life Railguns sound very different from those portrayed in Stargate (not to mention that there is no sound in space) - while the Stargate Railguns make a high-pitched firing sound, a real railgun produces a deafening, low-pitched boom when firing (a result of superheated gases expanding violently as the projectile leaves the turret).