ARC-920 railgun

The Asymmetric Recoilless Carbine-920, abbreviated ARC-920 or known simply as the railgun, is a compact-channel linear accelerator weapon used by the United Nations Space Command. It was designed and manufactured by Acheron Security.

Design details
The ARC-920 uses a pair of parallel conducting rails to accelerate its projectiles. A large electric current flows from one rail into the projectile and then to the other rail; the electromagnetic effects of this interaction accelerate the projectile to an immense speed. The rifle requires a brief charging period before firing high-explosive rounds accelerated to an incredible speed. The explosive yield contained in the round adds to the kinetic force of the impact, making the weapon effective against both infantry and armor. The weapon lacks a scope.

Gameplay
Compared to the Spartan Laser, the ARC-920's charging time is half the duration and deals less damage to vehicles. In addition, the travelling time for a fired shot is almost instantaneous. In Campaign and Spartan Ops, the charging time is longer than in War Games.

Tactics
Even though the weapon lacks zooming capabilities, one can zoom in using the suit's default 5x zoom and the weapon can be charged and fired with the zoom only being broken by the shot firing. This can be used to give greater precision to long-range shots. In Spartan Ops, the ARC-920 features the additional advantage that - unlike the Spartan Laser, Rocket Launcher and Sniper Rifle, a player can pick up additional ammunition from ammo crates, giving the player a potentially unlimited supply of ammunition.

Trivia

 * In canon, a magnetically accelerated projectile should be moving at multiple times the speed of sound. However, the railgun's projectiles move at a much slower subsonic speed; this is presumably for gameplay balance.
 * Despite being a railgun, the way that rings form around the barrel when charging and that the railgun kill medal depicting a projectile going through rings seem more indicative of a gauss gun.

List of appearances

 * Halo 4
 * Spartan Ops