The Magma Cannon is the primary armament of the Astra Militarum's Doomhammer super-heavy tank and is an immensely powerful Laser Weapon based on the same technology as the Volcano Cannon, designed to be able to destroy enemy Titans. The Magma Cannon is in essence a smaller version of the Volcano Cannon, which trades in its destructive power and range for a much higher rate of fire, which lessens the Doomhammer's efficiency as a Titan-killer but grants it tactical flexibilty. Hence, where a Shadowsword armed with the Volcano Cannon can easily operate as a lone Titan hunter, the Doomhammer must be supported by other elements of the Imperial Guard in order to bring a Titan down. Also, the Magma Cannon does not require the tank's engine to be stopped to fire, granting the Doomhammer the required mobility to bracket smaller targets and obliterate them. The Magma Cannon is powerful enough to severely damage a Titan with a single shot, but does not have the power of the Volcano Cannon to first punch through its Void Shields.
In addition, since the Magma Cannon is much smaller than the Volcano Cannon, the space freed up by removing the gargantuan capacitors necessary for firing the Volcano Cannon can be converted into a hold capable of transporting a small platoon of Imperial Guardsmen, or upgraded to serve as a cramped but fully functional field headquarters, equipped with powerful Vox-casters and tactical arrays. This allows an armoured regiment's commander to both lead his troops and participate in the fighting if he commands a Doomhammer.
- Codex: Astra Militarum (8th Edition), pg. 54
- Imperial Armour Apocalypse II, pg. 11
- Doomhammer Datasheet - Games Workshop
- Warhammer 40,000: Apocalypse (6th Edition), pp. 140-141