A Gauss Cannon is type of horrifying Necron Gauss Weapon that can strip a target down molecule by molecule, reducing it to its constituent atoms in a matter of seconds. Gauss Cannons are larger than the more common Gauss Flayers and Gauss Blasters, and feature four barrels which lead to transparent tubes containing the unholy and unknown viridian energy the weapon fires, and an axe-like bayonet underneath the muzzle.
Unlike more conventional directed energy weapons, a Gauss Cannon does not deliver a cutting beam or pure bolt of electromagnetic force or subatomic particles. Instead it emits an emerald, lightning-like molecular disassembling beam capable of reducing flesh, armour and bone to almost nothing. In the case of more powerful Gauss Weapons, this process occurs so rapidly and completely that the emerald beam of energy may appear to punch through its target, though it may be more accurate to think of it as "digging" its way through armour. It is said to be extremely painful to be shot with a Gauss Cannon, and victims die as much from the systemic shock of the assault as the damage caused by the beams.
Gauss Weapons have been known to hurt monstrous creatures that similar weapons have no hope of even scratching, and have also been documented tearing at the armour of even the most heavily armoured of tanks and starship hulls with ease. The Imperium of Man is confounded by the nature of the energy used by these weapons, not only because the basic weaponry of the Necrons can cause great harm to even the most advanced vehicles deployed by the armed forces of the Imperium, but also because by all the physical principles known, these weapons should overheat and malfunction as a result of the tremendous energies they unleash, destroying the warrior who is firing them.
Gauss Cannons fire more powerful beams than Gauss Flayers, and are more similar to Gauss Blasters in strength. However, Gauss Cannons have a better capability to be fired on the move, and shots from Gauss Cannons also contain greater armour penetration abilities; being able to rip through even Astartes Power Armour with ease. They are extremely potent against infantry and light vehicles alike. Gauss Cannons are most commonly used by Necron Destroyers as their standard armament. However, both Catacomb Command Barges and Annihilation Barges are able to mount an underslung Gauss Cannon instead of their usual Tesla Cannon. Tesseract Arks are also able to mount two Gauss Cannons as secondary weapon systems.
At their most basic level, Gauss Weapons can be described as linear induction motors. When fired, they appear to produce focussed bipolar magnetic fields so that anything the weapon is targeted at, such as a human body, will be "pulled" (at the sub-atomic level) towards the gun. Gauss Weapons appear to pulse with intense electrical currents, which form the potent magnetic fields that strip the target's constituent atoms even as the target is attracted towards the weapon.
The design of a Gauss Weapon, with all its parameters kept dynamic to achieve maximum efficiency, is a seeming mathematical impossibility. The greatest problem encountered by the Magi of the Adeptus Mechanicus in replicating Gauss Weapon design is devising a means to safely generate and release the power of the energy discharge, which runs in the multi-megawatt range. Because the power required for Gauss Weapons is extremely high, even microscopic imperfections in their design will generate massive energy losses. If a mechanical trigger is used to deliver the firing pulse, the moment the firing mechanisms come into contact, microscopic irregularities in the material will dissipate so much energy as to completely vaporise the gun and its user. If the trigger then somehow manages to close, the vaporised surfaces and the molten metal beneath them weld together, and the trigger is thus ruined. How the Necrons overcome this technological conundrum is unknown. Assuming these firing difficulties can be overcome, the final effect would be a beam capable of stripping a target down it its constituent atoms extremely rapidly, which is what Imperial forces have witnessed on the battlefield.
Extensive study by the Imperium of Gauss Weapons and their effects on both organic and inanimate matter has, thus far, been hampered by the lack of a working device to examine. Investigations into the remains of Necron troops and their equipment reveal a fascinating level of interaction between the Gauss field and the target's atomic structure. It appears that the unknown energy field generated by the weaponry is capable of breaking the bonds of the target material at a sub-atomic level and energising them with an opposing magnetic charge to that generated by the weapon itself. This accounts for the "flaying" effect noted in many after-action reports from Imperial commanders in the field. As each layer of skin or muscle is exposed, it is broken down by the weapon's beam and carried towards the gun. This obviously results in catastrophic failure of the biological components involved and their dissipation into vaporous form.
- Codex: Necrons (3rd Edition), pp. 14, 54-55
- Codex: Necrons (5th Edition), pp. 81, 91, 94-95
- Codex: Necrons (7th Edition) (Digital Edition), pg. 199
- Deathwatch: The Outer Reach (RPG), pg. 119
- Imperial Armour Volume 12: The Fall of Orpheus, pg. 124