- "Someone get on that turret!"
- —Dominic Santiago, to his fellow Gears, aboard an Assault Derrick during Operation: Hollow Storm
The Chain Gun was a large, high-caliber, electrically-cycled, fully automatic, heavy gatling gun employed by the Coalition of Ordered Governments military. It was usually mounted as an offensive weapon on vehicles, such as the King Raven and Assault Derrick, and was seen on the Tyro Pillar. It could also be used as a stationary emplacement gun on fortifications for defense. It employed the Gatling-gun principle, in which six revolving barrels rotate around the firing axis. This arrangement allowed the individual barrels to cool between shots.
The Chain Gun's action was driven by an electric motor, unlike the hand-crank system of the Mulcher. This feeds ammunition and rotates the firing mechanism. As it rotates, the barrels close into the bolt for firing, then withdraw to extract the spent cartridge case and feed in a fresh round. The entire process happens very quickly; when the Chain Gun is fired, the sounds of the individual shots blur into a continuous, rippling roar.
Much of the Chain Gun's length was in its barrels; the actual firing mechanism is quite compact for such a powerful weapon. The weapon only had rudimentary iron sights; the gunner is expected to observe the weapon's bullet spray and adjust their aim accordingly. To keep up with the Chain Gun's voracious appetite for ammunition, it was normally fed from enormous ammunition boxes, with ammo fed to the weapon via a flexible metal chute.
Because of the Gun's size and mass, it was far too big to be moved by any soldier. Instead, it was normally seen as a vehicular or aircraft weapon - it was particularly well-suited for being a helicopter door gun - with its high rate of fire making up for the relative lack of accuracy that came from using a flying helicopter as a firing platform. It was also sometimes seen mounted on a tripod or base for use as a powerful defense weapon.
The Chain Gun was the COG answer to the Locust Troika. Though it's not quite as powerful as its Locust contemporary, it was still an incredibly powerful weapon that could tear even the most brutal of enemies to shreds.
In general, the Chain Gun is functionally identical to the Troika. It isn't as powerful (since it fires fewer bullets), but it's considerably more accurate. Like the Troika and Mulcher, it uses a cooling system that can flush the weapon with coolant should it overheat. Note that, because the Chain Gun, like the Troika, is electrically-operated, its clutch stops the barrels cold if you stop firing to flush the gun with coolant. Because of this, it's advised that if you must stop firing, completely reduce the gun's heat before starting it back up.
Destruction of Halvo Bay 
Several Chain Guns were mounted at various COG outposts during the Destruction of Halvo Bay, like the Museum of Military Glory, the Halvo Bay Military Academy, Onyx Point and the Courthouse, amongst others. However most of these posts were captured by the Locust and they used the Chain Guns to take down any Gear that came nearby - more proof of how the Locust Horde could adapt and use any weaponry at their disposal. Some of these turrets had a frontal shield to protect the gunner from enemy fire. Kilo Squad was forced to deal with several of these outposts on their way to the Lightmass Missile, and even managed to capture and use some of them against their temporary owners.
Evacuation of Ilima
Zeta-Six used a Chain Gun against a horde of Locust that came out of an E-Hole near their evacuation outpost. They managed to hold off many Locust, but more E-Holes soon spawned and Reavers joined the fight. The Chain Gun was destroyed by the Locust, and Lt. Minh Young Kim was forced to use the Hammer of Dawn to stop the Locust.
More Chain Guns were used by COG forces against General RAAM and his squad, which was comprised of a Theron Elite, a Tremor and two Mauler Elites. Despite their firepower and numbers, the Gears were unable to stop RAAM's forces from getting through several outposts and using the Tremor's Thumper to call several Seeders to ink the skies of Ilima so that it could be devoured by the Kryll.
In the final stages of the Lightmass Offensive, Marcus Fenix used a Chain Gun mounted on the roof of the Tyro Pillar to fend off attacking Reavers. Another Chain Gun was used by Dominic Santiago in the battle with the notorious General RAAM before the Locust General was killed by the pair.
Operation: Hollow Storm
During Operation: Hollow Storm, Chain Guns were mounted on the Assault Derricks to protect them on the road to Landown. On board Rig 314, Sgt. Fenix used the turret to shoot down attacking Nemacyst and scores of Reavers. Further along the road to Landown, the turrets were used to fend of attacking Grapplers and even Brumaks.
Chain Guns were used again during the Locust Siege of Jacinto, where Dominic Santiago and Marcus Fenix used the weapon for repulsing an attack by a swarm of Reavers on the Comm Tower at Wrightman Base.
During the Savage Locust attack on Anvil Gate, the defending Gears used the turrets on the front wall to beat back the attackers. However, after the Locust overran the front gate and gained more ground inside the Fort, the Gears opened up with two more turrets. The confined area of the courtyard made it easier for the defenders to destroy the enemy.
At Endeavour Naval Shipyard, several Locust attempted to use Chain Guns and Troikas to stop the newly arrived Gears. Their attempt failed to stop them and the Gears managed to use some of them to deal with their attackers.
Behind the scenes
- In Gears of War 3, Horde 2.0, it is unknown why the COG use Troikas, since they are Locust weaponry instead of the Chain Gun, since it is COG weaponry.
- In Gears of War: Judgment, there are upgraded Chain Guns with a frontal shield to avoid body damage in the campaign mode, similar to the Troika's shielded sides.
- Despite being named the 'Chain Gun', this weapon is actually a Gatling-type weapon. The difference between the two weapons is that a chain gun uses a single barrel and is chain-driven as opposed to operated by recoil or gas blowback. A Gatling gun, on the other hand, uses multiple barrels which revolve as the weapon fires, similar to the way a revolver's cylinder rotates as it is fired. A Gatling gun may be operated by any number of mechanisms, from electric motors to gas systems to simple hand cranks, and use relatively complex timing to ensure that each barrel and breech fires, loads ammunition, and ejects spent casings at precisely the right moment.
- In terms of functionality, the Chain Gun is very similar to the M61 Vulcan, which serves a similar purpose as a helicopter door gun, vehicle-mounted weapon, and defensive weapon emplacement for use against most soft targets, such as infantry, and lightly armored or unarmored vehicles.
- Gears of War: Judgment
- RAAM's Shadow
- Gears of War (First appearance)
- Gears of War: Ultimate Edition
- Gears of War 2
- Gears of War 3
- Gears 5