Chaingun/Doom (2016)

"Designed for sustained volleys, the Chaingun deals high damage at a very high rate of fire."

- Arsenal description

Delta-12 Chaingun, or simply Chaingun, is a weapon featured in Doom (2016). Serving as a heavier-duty alternative to the Heavy Assault Rifle, the newest incarnation of the classic weapon features an extremely high rate of fire with its famous six-barreled design.

Campaign
""The Delta-12 Chaingun (often referred to as "The D12" by operatives), is a high velocity heavy weapon capable of suppressing multiple targets at once. Recent changes to the firing mechanism have pushed the Delta-12 to the physical limits of a ballistic weapon. An Argent infused piston compresses gas within the firing crucible to over 220,000 PSI. When released, this launches a 15mm Tungsten Slug with a muzzle velocity of nearly 5,000 feet per second. The heat generated by this action is siphoned into a thermal gel compound that automatically recharges the 96volt battery pack. This allows the weapon to sustain an almost endless firing cycle, as long as ammunition is present. The Delta-12 Chaingun weighs 45kg, making it a lethal but cumbersome armament.""

- Codex Entry The newest incarnation of the Chaingun functions somewhat like a fusion of the 1993 and 2004 incarnations; the weapon will begin firing as soon as the trigger is pulled, but the weapon still requires a period to spool, during which it'll start off firing slowly and gradually accelerate to maximum speed.

Gameplay
The newest incarnation of the Chaingun functions somewhat like a fusion of the 1993 and 2004 incarnations; the weapon will begin firing as soon as the trigger is pulled, but the weapon still requires a period to spool, during which it'll start off firing slowly and gradually accelerate to maximum speed.

Compared to the Heavy Assault Rifle, the Chaingun has a much larger reticle and wider spread, making it inaccurate at long ranges. However it shoots at a much faster rate, of 900 RPM or 15 shots/sec, ammunition pool can be consumed quickly when firing without discipline, even more so with the use of the Mobile Turret modification. Thus, the weapon is best reserved for close-to-medium range fights against either large groups of enemies or a single large target, as the inaccurate storm of higher-damage rounds would be wasteful against small groups or targets.

An unfortunate quirk about the Chaingun is that the player's mouse sensitivity and thus, their ability to aim quickly, is lowered while the weapon is firing and/or its barrels are spinning. Thus, using the weapon on fast targets such as Imps or Summoners may require taking one's finger off the trigger to re-position their aim.

Ammunition
The Chaingun shares its ammo pool with the Heavy Assault Rifle. The player can increase the max ammo cap by using Argent Cells and allocating its power to "Ammo" subsystem.

Modifications
Keeping in-line with Doom 2016's use of weapon mods, the Chaingun has two of its own:

Gatling Rotator
"This 3rd party modification overrides the crucible release safety, allowing the weapon to fire immediately without waiting for maximum rotation. This action, while allowing for instant use, does prolong the time it takes to reach full speed. This modification is unapproved by the UAC."

- Gatling Rotator Codex Entry

The Gatling Rotator gives the weapon the ability to preemptively spin itself up without firing by holding the weapon mod button, allowing one to enter a fight with the weapon already able to fire at full power. While this mod is simple, it has little creative application compared to its alternative. Visually, this mod attaches a small motor to one side of the weapon.

Mobile Turret
"A secondary firing crucible and compression chamber can be added to the weapon. This modification unbalances the weapon, so remaining stationary while firing is recommended. When used, the weapon fires at twice the normal rate of fire, expending twice the ammunition and superheating the muzzle. Although this modification presents the most powerful suppression in the UAC arsenal (other than the BFG prototype project), the system can and will overheat if not used cautiously."

- Mobile Turret Codex Entry

The Mobile Turret gives the weapon the ability to "unfold" into a triple-barreled minigun by holding the weapon mod button, giving it near-pinpoint accuracy and almost tripling the rate of fire. As a trade-off, the weapon causes the player to move slower when firing, chews through ammo even faster than it does already, and (without its mastery upgrade), eventually overheats when fired for too long. Visually, this mod replaces the standard sextuple barrel with a cluster of three tri-barrels that fold into a triangular shape when the Chaingun is fired normally.

Multiplayer
The Chaingun can be unlocked in the multiplayer at level 2 (it's also available to use in level 1 by choosing "Ambusher" default loadout). The player spawns with 125 bullets (200 is the max ammo). The weapon features two fire modes:
 * Primary Fire - A large drum-fed rotary machine gun with a high rate of fire.
 * Weapon Mod - Spins up the rotating barrel assembly to its maximum speed (Hold the Weapon Mod button).

In multiplayer, the fire-rate is staggered; producing a mean RPM of 900 with repeated high-speed two-round bursts done at 1800 RPM, and 450 RPM per burst.

Unlike its role in Singleplayer, the Multiplayer incarnation of the Chaingun serves as a single-target rapid-fire suppression weapon; thanks to the removal of aiming slower when firing but a lower damage per shot, the optimal way to use the Chaingun is to get close to an enemy and hose them down with bullets while carefully tracking them, something its in-built Gatling Rotator helps with.

While it is easier to aim with compared to other close-ranged weapons, it's arguably the weakest, taking much longer than the Super Shotgun, Combat Shotgun and Reaper to score a kill with. Thus, several players will replace the weapon with an alternative once earned.

Trivia

 * The weapon shares ammo with the Heavy Assault Rifle despite the fact that it uses 15mm tungsten slugs and the Heavy Assault Rifle fires 12.7mm rounds. The fact that they share the same ammo reserve in-game is likely a gameplay decision and not one of lore significance. With the chaingun being weapon 8 and the HAR weapon 4, it also better parallels the double-barreled shotgun (weapon 6) also sharing the basic shotgun's (weapon 2) ammo, and the Gauss cannon (weapon 7) using the plasma rifle's (weapon 3) ammo.
 * The Gatling Rotator description on the ingame Codex is inconsistent with the mod's actual function. It allows the user to spin the gun's barrels without firing, while the description states it allows the weapon to be fired "without waiting for maximum rotation". This implies that the Chaingun would originally be limited to firing only after spinning up the barrel to maximum speed, like the Doom 3 version.
 * Installing the Uranium Coating mod for the Gatling Rotator changes the Chaingun's firing sound, while installing the same mod for the Mobile Turret does not.
 * The barrels of the mobile turret resemble the tri barreled .50 Bmg Gau-19.