A Macrocannon is the largest member of the family of Auto Weapons and it has been used as a main armament on the warships of the Imperium of Man since the time of the Great Crusade in the late 30th Millennium. These massive ballistic weapons are deployed in batteries, and destroy their targets through the delivery of powerful broadsides of shells fired in volley to overwhelm their enemy in a barrage of destruction.
Macrocannons are giant, edifice-size weapons covered with gantries, cranes, power lines and pipes manned by a crew that stands hundreds strong. Macrocannons can also be deployed to serve as potent artillery weapons by Imperial ground forces, though such instances are rare as these weapons are not very mobile, and their range and accuracy drops tremendously when deployed within the confines of a gravity well and atmosphere, to the point that their massive firepower can present as much danger to friendly forces as to the foe.
Located upon the gun decks of voidfaring capital ships, projectile-firing Macrocannons require large crews to handle and load their enormous shells into the waiting breeches. First, the breech must be opened by one crew pulling on massive pinions or chains, while the second crew ready the next shell to be loaded. Once the breech is open, the spent casing is extracted and the breech quickly cleaned by the third crew, under the watchful eye of a junior Tech-priest or Enginseer who checks for any damage or impurity.
Next, the second crew loads the gargantuan shell into the breech, and quickly clears the way as the first crew starts closing the breech as soon as the shell is aligned with the barrel. Once the breech is closed and secured, the crews move to a safe distance waiting for the gun to fire and the loading cycle to start anew. Macrocannon crews also have to contend with sitting on top of a magazine full of enough munitions to level a city. Operating a Macrocannon is extremely taxing and tiring, and the sheer size and weight of the components makes any mishap that occurs almost always a fatal affair, crushing the life out of the poor wretches involved. Life expectancy amongst such crews is often measured in mere weeks.
Many starship captains still prefer the reliability of Macrocannons despite the medieval toil they inflict on the crew of their warship. Additionally, Macrocannons are far more robust than energy weapons like Lances. After it suffers punishing damage, a Macrocannon can still load and fire long after an energy weapon's delicate mechanism would fall silent. Macrocannons tend to be mounted in individual gunrooms to contain the damage if their magazine explodes. Each cannon's battery is led by a gun captain and each gun deck by at least one petty officer. An ensign or lieutenant has nominal charge of the gun deck but these junior officers are seldom seen away from the vessel's command decks. The battery's commanding officer is usually only heard as a disembodied voice over the Vox-caster by the battery's crew.
- Disruption Macrocannon - This Macrocannon variant fires a "shell" of highly charged, ionized deuterium atoms. These particles cause minimal physical damage to their targets. Instead, they are intended to overload and shut down power transfer systems throughout the target vessel. These weapons are particularly useful for vessels that need to capture their prey intact.
- Disruption Macrocannon Broadside - These are larger variants of the Disruption Macrocannons, which are mounted on a warship's extended broadside.
- Hecutor Pattern Plasma Macrocannon - The Hecutor Pattern plasma battery is an ancient variant of plasma macroweaponry that fires superheated plasma rather than a ballistic shell. This variant refocuses the power of the plasma "blast," concentrating it into a compressed photonic packet that can be fired over extremely long distances. It is rare to see these weapons on any but the oldest Imperial vessels, meaning many are found on Heretic vessels lost to the Forces of Chaos millennia ago.
- Mark VI Mars Pattern Macrocannon - The most common macrobattery, these Macrocannons are reliable, hard-hitting weapons that fire kilotonne-grade ordnance, mounted along an Imperial warship's dorsal ridge or in a broadside.
- Stygies Pattern Bombardment Cannon - As the name suggests, this devastating weapon is designed to reduce planetary defences to rubble and support Imperial military landings on target worlds. Most often the Stygies Pattern Bombardment Cannon uses a linear accelerator to launch massed salvoes of heavy magma bomb warheads, and though it is relatively short ranged, the Bombardment Cannon can also be used in naval combat. Often the simple rumour that orbiting Imperial vessels carry this weapon is enough to force a quick surrender.
- Stygies Pattern Macrocannon - This variant of the Macrocannon is designed to fire heavier ordnance than the Mars Pattern. These alternative shells contain an adamantium core that cuts through the heaviest known forms of starship armour.
- Thunderstrike Macrocannon - An older version of the Mars Pattern Macrocannon, these Macrocannons lack the range and power of the later Imperial variants. They are most often found on transport vessels.
- Deathstrike Cannon - An example of an artillery-grade Macrocannon, this weapon is by starship standards a relatively small Macrocannon. The Deathstrike Cannon is installed as a baseline weapon in the Warlord-class Battle Titan, with the barrel jutting from the shoulders of the massive walker where the head of the Titan normally resides.
- Lathe Pattern Grav-culverin Broadside - The strange orbital dance of the three planetoids that make up the Lathe Forge Worlds has given the Adeptus Mechanicus Magi there a unique insight into the ancient art of grav-weaponry, using strange forces to hurl warheads at tremendous speeds. Due to the unique methods of propulsion, variant warheads can also be fired through the grav-culverin, including self-propelled ordinance for greater range.
- Mezoa Pattern Macrocannon - The Forge World of Mezoa has long advocated a modification of the standard Mars Pattern Macrocannons to increase damage at the cost of range and space aboard a voidship.
- Pyros Melta-cannon - These squat, oversized, and highly-insulated Macrocannons are designed specifically to fire shells tipped with powerful melta-charges that detonate with furious heat.
Ork starships are more heavily armed than Imperial vessels of comparable size. Massive batteries of Macrocannons dot the hulls of every Ork warship, turrets and barrels protruding from every gap in the ship's hull that are capable of battering through an enemy vessel's Void Shields and ripping large chunks out of its hull. In a matter of minutes, an Ork vessel can unleash thousands of shells at a target, filling the void around an enemy ship with debris, shrapnel and unexploded shells. Above all other weapons, Orks favour massive shell-hurling Macrocannons, referred to collectively as "Gunz." Grouped together into batteries, these weapons fire volley after volley of solid shot and explosive shells, overwhelming any enemy in a torrent of destruction. However, these weapons do not always work as desired, sometimes misfiring or jamming. They may also be deactivated for repairs or "improvements" by a bored Mekboy. The following is a list of the most common "Gunz" found aboard Ork spacefaring vessels:
- Gunz - The most common Ork Macrobatteries are referred to simply as Gunz. Though this encompasses any number of different types of ship-based weapons, most fire ballistic projectiles of some sort or another. It is fairly common for Orks to loot weapons from defeated vessels, so many Gunz are "improved" versions of standard Imperial Macroweapons. The Ork inclination towards firepower is such that any gap in the haphazard armour plating of a Greenskin warship is soon filled with a Gun.
- 'Eavy Gunz (Kannonz) - Alongside more conventional Macrocannons, the Orks commonly employ short-ranged but extremely powerful ballistic cannons called 'Eavy Gunz or Kannonz. Firing dense slugs of scrap metal massing thousands of tonnes, as well as jury-rigged plasma bombs, these shells quickly become inaccurate over long range. Nevertheless, they cause terrifying damage at close range. Often rebuilt from the largest broadsides of Imperial Cruisers, these guns protrude menacingly from the scowling armoured prows of Ork Kill Kroozers, ready to unleash salvoes of heavy explosive shells. Kannonz often have extra-long barrels, so the shells will fire further.
Aeldari Starship Weapons
The Aeldari disdain the use of crude ballistic weaponry like Macrocannons on their starships, preferring elegant and deadly laser and plasma-based weapons that can prove devastatingly accurate.
- Rogue Trader: Core Rulebook (RPG), pg. 202
- Rogue Trader: Battlefleet Koronus (RPG), pp. 17, 34-35, 48, 75-76, 85
- Rogue Trader: Into the Storm - The Explorer's Handbook (RPG), pg. 158
- Warhammer 40,000: Rogue Trader (1st Edition), pg. 87
- Execution Hour (Novel) by Gordon Rennie, pg. 9-62