It is an ancient weapon, but has nevertheless remained a widely-used piece of wargear throughout the Imperium's history. These rapid-firing weapons can lay down a burst of fire to cover advancing troops, or strafe enemy-held positions.
Autocannons are considered ideally suited for attacking enemy vehicles and fortifications from long range. Though they lack the heavy punch of a Lascannon, they can fire more rapidly and are less prone to overheating. However, the need to carry large amounts of ammunition is a distinct disadvantage. This weapon is also very large and ungainly. This bulk, combined with the serious recoil it creates, often restricts an Autocannon to a vehicle mounting or to use by dedicated Heavy Weapons Squads.
Autocannon shells once contained an explosive charge similar to that of a bolt (only far larger) though the means of producing this charge has been lost to Imperial science and now the rounds fired by an Autocannon are less powerful than they once were. However, the Autocannon is still more than capable of eliminating heavily armoured infantry or light vehicles, and is employed by Astra Militarum fire support weapons teams due to their versatility and reliability.
Though Autocannons are designed to be fired from a standard pattern bipod with a steel glacis, in extreme situations it is not unknown for some of the physically stronger troops to carry them into battle slung from a suspensor harness, though this "gung-ho" method of firing is unusual and not encouraged.
Surprisingly, the Autocannon is almost ignored as a weapon by the warriors of the Adeptus Astartes. While their superhuman physique and Power Armour-augmented strength allows a Space Marine to carry and fire an Autocannon with ease, the large majority of Loyalist Chapters favour either ranged weapons with a much higher rate of fire (like the Heavy Bolter or Assault Cannon), or ranged weapons packing more killing power with each individual shot (like the Lascannon or Multi-melta).
As such, the Autocannon is a rarely fielded weapon for the Space Marines. However, the Heretic Astartes who have thrown in their allegiance with the Ruinous Powers do make ample usage of the Autocannon, as it is a simple and sturdy weapon requiring very little of the heavy maintenance that most Chaos Space Marine warbands now lack the resources to execute.
Known Imperial Autocannon Patterns
- Agrippina Pattern Mark II - A common pattern of Autocannon utilised by the Astra Militarum.
- Gryphonne IV Pattern - Formerly manufactured on the now devastated Forge World of Gryphonne IV, this pattern of Autocannon is often utilised on the Salamander Scout armoured reconnaissance carrier. Ammunition for this smoothbore gun is fed automatically through a four-round feeding tray, and extra ammunition is dropped into the tray by hand. Other features of this pattern include recoil dampeners, electronic sighting and rangefinding.
- Herakles Pattern Accelerator Autocannon - This ancient pattern of Heavy Autocannon was only ever found mounted upon Sicaran Battle Tanks. These rapid-firing weapons fired shells at a much higher velocity than a standard Autocannons, enabling them to successfully engage moving targets and strike with pinpoint accuracy.
- Ironhail Autocannon - The Ironhail Autocannon is a Dreadnought-sized Imperial Autocannon that is deployed on the Invictor Tactical Warsuit as a primary weapon. The Ironhail Autocannon allows an Invictor walker to unleash a punishing hail of ballistic firepower at relatively close ranges.
- M34 Autocannon - The M34 Autocannon is an older version of a common Imperial Guard pattern, and is used throughout the Calixis Sector. It uses a tripod mount and can be manned by one person, though it ideally employs a crew of two to move, set up, and assist with reloading the weapon.
- "Six/Twelve" Mauler Cannon - An adaptation unique to the Spinward Front, the Mauler Cannon is actually a modified twin-barrelled M34 Autocannon designed specifically for use by Ogryns. Rebuilt with a heavier frame, shorter barrels, a fire-limiter, larger handholds, and a triple harness capable of withstanding an Ogryn’s strength, the Mauler Cannon gives Ogryn units an enormous boost to their firepower. Sadly Mauler Cannons have picked up the nickname “Six/Twelve” by regular Guardsman, referring to the number of shots an Ogryn will likely fire before they somehow break it or decide to use the weapon as a club.
- Syrtis Pattern Autocannon - A commonly used pattern of Autocannon mounted on Predator Destructor tanks.
- Accelerator Autocannon - These rapid-firing weapons fire shells at a much higher velocity than a standard Autocannon, enabling it to successfully engage moving targets and strike with pinpoint accuracy. A smaller version of these weapons are used by Primaris Marine Vanguard Suppressors.
- Icarus Autocannon - The Icarus Autocannon is a type of large Autocannon utilised commonly on Imperial anti-aircraft arrays as well as by Imperial Knights. On Imperial Knights, it is linked directly to the pilot's mind via the Throne Mechanicum and can track down and destroy incoming enemy aircraft.
- Armiger Autocannon - The Armiger Autocannon is a type of Autocannon wielded by Armiger Helverins. The Armiger Autocannon has a high rate of fire and is capable of laying down hundreds of armor-piercing shells per solar minute.
- Reaper Autocannon - The Reaper Autocannon is a type of Autocannon used predominately in the 41st Millennium by Chaos Terminators. However at the time of the Great Crusade and Horus Heresy they were common in the arsenals of all the Legiones Astartes. Originally designed as a support weapon for Tactical Dreadnought Armour, the Reaper is a compact, rapid-firing Autocannon which depends on the strength of Terminator Armour to stabilise the weapon and cope with its massive recoil.
- Cthon Pattern Autocannon - The Cthon Pattern was a type of Autocannon deployed by Terminators during the Great Crusade and Horus Heresy eras.
Although the Autocannon is quite common, its popularity is rather inconsistent. Many Imperial commanders shun use of the Autocannon, maintaining that it serves no role fully. It lacks the firing rate of a Heavy Bolter or Multi-Laser, meaning that its anti-infantry role is limited. It also lacks the sheer armour-piercing strength of a Krak Missile or Lascannon, and thus cannot be deployed to destroy enemy armour.
However, although many disapprove of the Autocannon, there are just as many who hail it as a tactically vital weapon. Its supporters argue that its versatility is its best attribute; that it can in fact be useful against both infantry and armour. Although it cannot tear through ranks of infantry like an Assault Cannon can, or bring down enemy armour to the extent of a Lascannon, it can still support an army in any tactical situation.
However, it is against the Tyranids that the Autocannon finds its true calling. The ability to deliver large volumes of heavy firepower is vital in combating massive Tyranid bioforms such as Hive Tyrants and Carnifexes, which lack the natural armour that requires the penetrating power of a Lascannon, but are too tough to be threatened by a Heavy Bolter.
The Autocannon is a relatively simple weapon; it is mass-produced in the manufactoria of Imperial Hive Worlds and Forge Worlds. It is a large weapon, and is far too cumbersome to be carried with its ammunition by one man. As a consequence, the weapon is usually mounted on vehicles. However, in the Astra Militarum, Autocannons are often operated by teams of two soldiers. This is a manageable arrangement; one trooper mans the gun itself while the other loads the ammunition. Man-portable Autocannons are usually fitted with a small blast shield to provide some protection to the crew from incoming fire.
Uses within Imperial Armies
The Astra Militarum generally makes heavy use of the Autocannon. This usage does of course vary, depending on a given regiment's tactical preferences. It is frequently used with:
- Leman Russ Exterminator, a variant of the Leman Russ Main Battle Tank
- Heavy Weapon Squads
The Imperial Navy frequently equips its light fighter aircraft with Autocannons. The light-armor-piercing and semi-rapid fire characteristics of the weapon perfectly suit the Navy's snub fighters in dogfighting situations.
The Lightning fighter craft in particular employs this weapon to great effect. The Navy commonly mounts the Autocannon on:
The Autocannon is not used as widely in the Adeptus Astartes as it is in other branches of the Imperial armies. Being an elite and fast-moving army, the Autocannon has fallen out of favour with them, and weapons such as the Lascannon or Heavy Bolter are preferred.
However, due to the Autocannon's versatility, most Chapters still retain a few examples in their armoury. Many Terminators carry them, as these ultra-heavy troops can move and fire an Autocannon one-handed and still carry out direct assault.
The weapon, as noted above, is far more popular with Chaos Space Marines, particularly those drawn from Renegade Chapters. Autocannons are frequently used with:
- Reaper Autocannon - The Reaper Pattern Autocannon is a particular type of double-barrelled Autocannon no longer employed by the forces of the Emperor. It is often seen amongst the ranks of Chaos Terminators, who use the heavy volume of fire it lays down to great effect, giving Chaos Space Marine warbands an ability to take out heavy troops and light armour at range.
- Syrtis Pattern Autocannon - This pattern of Autocannon is commonly utilised on the Predator Destructor.
- Hades Autocannon - The Hades Autocannon is most frequently used by the monstrous Daemon Engines of the forces of Chaos, specifically the Heldrake and Forgefiend. Hades Autocannons possess six barrels and each can sustain a high rate of fire capable of tearing through massed infantry and well-armoured targets with ease. Hades Pattern Autocannons also have increased damage potential per shot compared to the standard Imperial Autocannon. It is a weapon that the Imperium of Man has come to fear just as much as the hideous creatures that wield it.
- Black Crusade: Core Rulebook (RPG), pg. 156
- Codex: Chaos Space Marines (6th Edition), pp. 36, 65, 102
- Codex: Space Marines (8th Edition) (Revised Codex), pp. 81, 138
- Codex: Space Marines (5th Edition), pp. 59, 61
- Codex: Chaos Space Marines (4th Edition), pg. 82
- Codex: Imperial Guard (5th Edition), pg. 68
- Codex: Imperial Knights (7th Edition), pg. 116
- Dark Heresy: The Inquisitor's Handbook (RPG), pp. 114, 175
- Imperial Armour Volume One - Imperial Guard and Imperial Navy, pg. 131
- Imperial Armour Volume Two - Space Marines and Forces of the Inquisition pg. 29
- Imperial Armour Volume Four - The Anphelion Project, pp. 116, 118
- Imperial Armour Volume Five - The Siege of Vraks - Part One, pg. 97
- Imperial Armour Volume Six - The Siege of Vraks, Part Two, pg. 148
- Imperial Munitorum Manual, pg. 70
- Only War: Shield of Humanity (RPG), pg. 127
- Rogue Trader: Faith & Coin (RPG), pg. 82
- The Horus Heresy Book Three: Extermination (Forge World Series) by Alan Bligh, pg. 119
- Warhammer 40,000: Rogue Trader, pg. 82
- Warhammer 40,000: Wargear (2nd Edition), pg. 34
- Nightbringer (Novel) by Graham McNeill, pg. 169
- Forge World - Sicaran Battle Tank