Its most notable feature is its incredibly high rate of fire, easily eclipsing that of the autocannon it replaced. It is a medium-calibre rotary autocannon, with 6 barrels cycled by an electric motor past a single chamber.[Needs Citation]
The weapon was developed after the Horus Heresy as a replacement for the autocannon and Rotor Cannon, which had been a common heavy weapon on Terminator suits until then. Introduced during the mark 3a phase of Terminator armour development, this weapon is the standard alternative to the heavy flamer as a squad's special weapon. Its design has changed little, retaining the distinctively long, cylindrical, rotating barrels.[Needs Citation]
Although it lacks the range of the autocannon and many other heavy weapons, the assault cannon is a fearsome weapon when used in the close range role it was designed for. The weapon is prone to overheating and jams due to its high rate of fire - the number of rounds fired per second are counted in the hundreds. The barrels and other firing components are made of a heat-dispersing ceramic/metallic alloy, helping the weapon to withstand the intense heat generated by its high rate of fire. Despite this, the barrels still reach temperatures of over 300°. Due to the high rate of wear on the barrels, the barrels are replaced after every mission. Motor and barrel failure are common problems with the assault cannon, making the weapon prone to jamming during sustained bursts. The weight and complexity of the mechanism, and the heavy recoil generated means that the assault cannon requires a stable firing platform. The weapon is not considered man portable, however the powerful servos, recoil compensators and stabilizers built into Terminator armour allows the elite Astartes Terminator squads to carry the weapon into battle. The assault cannon is well suited to the battlefield role of Terminator squads, providing a massive rate of fire which often compensates for the enemies' vast superiority in numbers. In confined environments providing long corridors of fire, such as space hulks and hive worlds, the assault cannon is invaluable.[Needs Citation]
The high rate of fire makes the assault cannon unsuitable for extended engagements when used by Terminators, as the ammunition carried is quickly exhausted. This drawback is negated in vehicle and Dreadnought mountings, where ammunition storage capacity is far greater. The standard ammunition fired is a cased round, comprising a dense metallic core covered in a non-metallic composite sheath with a diamantine tip. This provides excellent penetration capabilities against light and personal armour.[Needs Citation]
It has long been reported by the Astartes that the assault cannon's massive rate of fire can allow it to chew through armour that would normally be impenetrable to a weapon of its calibre. Extensive testing by the Adeptus Mechanicus supported this observation, and Astartes targeting doctrines have been officially amended to recognize this attribute. The logistic shortcomings of the assault cannon are far outweighed by its destructiveness in combat and its effect on enemy morale.[Needs Citation]
- Absinia Pattern - Used by the Sons of Medusa during the Badab War.[7b]
- Absolo Pattern - Used by the Red Scorpions during the investigation into Beta Anphelion IV.
- Kheres Pattern — Great Crusade-era prototype. Used by Contemptor Pattern Dreadnoughts in the Great Crusade, it was being phased out by more compact designs wielded by Terminator squads by the start of the Horus Heresy.
- Iliastus Pattern — Great Crusade-era prototype designed by The Dyzanique. A more compact and portable variant of the highly successful Kheres pattern, the pattern boasts formidable firepower, but is prone to catastrophic failure. Used by the Imperial Fists and Blood Angels.
- Mk I Pattern — A pattern used by the Man of Iron UR-025.
- Ultima Pattern - Used by the Dark Angels during the Siege of Vraks.
- 1: Scions of the Storm (Short Story) — Tales of Heresy (Anthology), pg. 207
- 2: Codex: Space Wolves (5th Edition), pg. 59
- 3: Warhammer 40,000 6th Edition Rulebook, pg. 54
- 4: The Horus Heresy Book One - Betrayal pg. 239
- 5: The Horus Heresy Legiones Astartes: Age of Darkness Legions pg. 29
- 6: Imperial Armour Volume 4, pg. 114
- 7: Imperial Armour Volume 10
- 8: The Horus Heresy Book Three - Extermination, pg. 267
- 9: Imperial Armour Volume 5, pg. 148
- 10: Forgeworld Iliastus Pattern Assault Cannon (last accessed 11/8/2023)
- 11: White Dwarf 128 (2016), pg. 8 Contemptor Dreadnought
- Warhammer 40,000 3rd Edition Rulebook, pg. 61
- Codex: Dark Angels (4th Edition)
- Warhammer 40,000: Wargear (2nd Edition)
- Warhammer 40,000: Compendium
|Slug-Throwers||Stub gun • Hand Cannon • Stub Rifle • Heavy stubber • Shotgun • Ripper Gun|
|Auto-Weapons||Autopistol • Autogun • Autocannon • Assault cannon • Macro cannon|
|Ork||Grot Blasta • Slugga • Shoota • Big Shoota • Supa-Gatler • Gigashoota|
|Eldar||Shuriken Weaponry • Shrieker Cannon • Death Spinner • Shadow Weaver|
|Dark Eldar||Splinter Pistol • Splinter Rifle • Splinter Cannon|
|Tau Empire||Kroot Bolt Thrower • Kroot rifle • Kroot hunting rifle • Kroot gun • Rail Rifle • Railgun|