I want to say thank you for the overwhelmingly positive response to my previous post! It inspired me to keep going and write this (probably-even-more-niche) companion piece.
(Note: I originally wrote this series on Reddit. This post has been very slightly edited.)
Today I'm going to apply similar methodology to my post about lasguns, autoguns, and boltguns to two other classic weapons that fill a similar niche: heavy bolters and heavy stubbers.
These two weapons have long had identical roles on the tabletop. In most editions, they had the same or similar class (heavy) and rate of fire, with heavy bolters coming ahead in terms of strength and armour penetration. In the latest full-size-40k rules, I believe heavy bolters deal more damage as well. In short: between the two, the heavy bolter is strictly an upgrade to the heavy stubber, which leaves the obvious question: "Why would anyone ever use a heavy stubber when a heavy bolter is available?"
(Note on methodology: as with last time, I'll be discounting questions of monetary and material cost of the weapons, as well as technical skill to manufacture. These are both valid reasons as to why a heavy stubber would be favoured over a heavy bolter, but I'll instead focus on ammunition weight and consumption. The reason for this is that it generates fairly 'hard' numbers that cannot be overcome with material abundance and technology. Any force, no matter how wealthy and sophisticated, is going to end up looking down the barrel of interstellar shipping at some point.
Ammo Consumption
Heavy stubbers are, I believe, literally intended to be .50cal machine guns, virtually unchanged from the 20th century. The ones that ship with the Imperial Guard Vehicle Accessory Sprue (the best sprue, change my mind) even bears a striking resemblance to the M2 Browning, introduced in WWI. This means we can directly slot-in the Pentagon's estimate of ammo use for .50 cal machine guns: 100 per day against ground-based targets, and 90 per day against aircraft.
Now, we have to ask which of these two estimates to use for the heavy stubber: ground-based, or anti-aircraft? In the currently-for-sale model range, the vast majority of heavy stubbers are pintle-mounted upgrades for Imperial Guard tanks. In fact, before Cawl's love-affair with the weapon, the heavy stubber was a 'signature' weapon of the Guard: other Imperial factions exclusively used storm bolters as pintle weapons. However, this is not the Guard's only use for heavy stubbers. Black Library novels, such as Dan Abnett's gob-smackingly-good Gaunt's Ghosts series, imply that heavy stubbers are sometimes used as squad-level support weapons (the titular Ghosts are more-often described with heavy stubbers than heavy bolters or autocannon), perhaps among lighter infantry than the Guard codex is intended to cover. Additionally, the Forgeworld model range makes liberal use of heavy stubbers, particularly among the Death Korps of Krieg, who use them widely as infantry-support weapons. Heavy stubbers also make frequent appearance among genestealer cultists, chaos cultists, renegades, and heretics, and among Necromunda gangs. These are all forces that in part supply themselves with PDf-or Guard-surplus (or "fell-off-the-back-of-a-Taurox") gear. I think we should then conclude that they are commonly-issued to infantry units alongside heavy bolters, even though this isn't represented in the codex, and that this restriction is primarily due to availability of for-sale models and game balance (on the tabletop, given the choice, you'd always pick the heavy bolter over the stubber).
Tank pintle mounts are considered anti-aircraft weapons, even though this rarely comes up on the tabletop. Pintle-mounted machine guns were historically used to give tanks a chance at fighting back against air raids, as unlike most turret-mounted weapons, they can swivel very quickly and have a very high maximum angle they can be aimed at. In fact, in the old 4e-era Apocalypse rules, pintle-mounted weapons had an accuracy bonus against flying targets in line with dedicated anti-air weapons. Similarly, anti-air Sabre Defence Platforms commonly mount four heavy stubbers. While a pintle-mounted heavy stubber isn't going to bring down a Manta any time soon, you can imagine them being used to plink away at various lighter flying threats with some success: gargoyles, jump-pack troops, jetbikes, gun drones, deffkoptas, and so on.
For this reason, pintle-mounted heavy stubbers will be given the 90 rounds/day estimate of anti-aircraft weapons, while other heavy stubbers (such as those used by cultists, gangers, Tanith and Death Korps heavy weapons teams) will be considered anti-ground weapons, and be allocated 100 rounds/day.
edit: as has helpfully been pointed out, the game term "heavy stubber" actually covers a much wider range of weapons that I'd initially assumed. Siege of Vraks, Part Two (2008), p149 has a closeup of a renegade's heavy stubber with some technical information (above). The book specifies that "heavy stubber" refers to any "heavy barrelled autoguns used for sustained fire," which is to say, anything that we'd currently call a machine gun. We can assume that vehicle-mounted heavy stubbers are generally .50cal (again, note the resemblance to the M2 Browning), but that those crewed by a single individual on foot (such as upgrades for cultists and the Death Korps) might be this lighter variety. I'll add the 8.25mm stubber to the tables, but note that most of my text analysis was written before this discovery. I'll use the Pentagon's estimate for .30 machine guns for ammo usage (150 rounds/day). If we scale up a 7.62mm round to 8.25mm (an increase of 1.17x), then the weight per round is 29.7g.)
Heavy bolters are obviously a bit more of a reach, as there's no "bolter, heavy" on the Pentagon's logistics tables. I think the closest analogue for a heavy bolter remains the .50cal, however, as they're used in a similar role: "very big guns that shoot very large rounds very quickly." On the tabletop, both are allocated the same rate of fire (3 shots per turn), though because 40k game stats compress a huge range of data into the same stat (see: a space marine and a Catachan having the same Strength score, even though clearly the marine would win in an arm wrestle), this isn't a precise indicator. However, even Necromunda, which has a much finer-grained rules-calibration than full-scale 40k (lasguns and autoguns are meaningfully different in Necromunda, for example), gives them both the same (very high) rate of fire: "Rapid Fire (2)," beaten only by exotic alien weaponry and twin-linked versions of the same. We can thus conclude that heavy bolters, despite their bulk and weight of their ammo, are intended to be very high-rate-of-fire weapons. For this reason, I will resist the (non-negligible) temptation to lower the heavy bolter's assumed ammo consumption in order to make the weapon seem more 'reasonable,' and instead see what some consequences might be of its implied 'unreasonable' (or 'frikkin rad') depiction. (ed note: I really like heavy bolters).
Heavy bolters, whether mounted on vehicles or carried on foot, are overwhelmingly used in anti-ground roles, so will always be given the 100 round/day estimate. For heavier anti-air weapons, the Guard prefers autocannon, such as those found on the Hydra.
So here's our first table: ammunition per weapon per day, month, and year.
rounds per day per month per year
8.25mm H. stubber: 150 4,500 54,750
.50 H. stubber: 100 3,000 36,500
.50 H. stubber (AA): 90 2,700 32,850
H. bolter: 100 3,000 36,500
Ammo Weight
Determining heavy stubber ammo weight couldn't be easier as these literally exist in the real world. I'll use the same .50cal mass estimate from the last post: 114g per round. For the lighter 8.25mm heavy stubber, I'll scale up a real-world 7.62mm round to 8.25mm (an increase of 1.17x), making the weight per round a svelte 29.7g
Heavy bolter ammo weight is more problematic. The wikia has an uncited claim that the heavy bolter fires .998 rounds (possibly where the claim that all bolters all fired .998 rounds that I saw while researching my last post originated). The wikia also claims (again, uncited) that heavy bolters fire the slightly-larger 1.0 calibre rounds. I'll press forward using .998 as standard, though if anyone can point me in the direction of a better source, I'd appreciate it.
.998" (25.34mm) roughly equivalent to 25mm, which is to say, the same calibre of round fired by an M242 Bushmaster autocannon, the gun turret mounted on the M2 Bradley. This is a very big gun that shoots very big projectiles, with each round weighing some 454g. I don't think we're intended to assume that a heavy bolter round is this large, however. The M242 Bushmaster, being an autocannon, would be represented by 40k's autocannon rules. With its higher strength and range, autocannon are clearly intended to fire more powerful rounds than the heavy bolter. Once again, bolt rounds are usually depicted as shorter and fatter than other types of ammunition, so let's say (arbitrarily) that a .998 heavy bolt round is ~75% as long (and therefore, as heavy) as an autocannon round, putting it at 340g per round. This may be due to the fact that bolt weapons rely less on penetration, and more on their internal explosives, and so are shaped to maximize internal volume rather than maximizing velocity and minimizing contact area (they're less pointy).
340g per round is still very heavy. Here's our table using this mass (including lasguns, autoguns, and boltguns from the previous article for comparison):
rounds per day per month per year
8.25mm H. stubber: 4.45kg 133.6kg 1,626kg
.50 H. stubber: 11.4kg 342kg 4,161kg
H. bolter: 34kg 1,020kg 12,410kg
Lasgun: [1.44kg--------------------------------]
Autogun: 0.15kg 4.6kg 56.14kg
Boltgun: 1.3kg 38.5kg 468kg
As you can see, logistics needs for heavy weapons massively outstrip those of the small arms examined in the last article. In fact, the mass of this ammo is actually greater than the small arms for the rest of the squad. Such is the scale of industrial warfare in the far future, I suppose.
Building a Regiment
Our hypothetical regiment from the previous article consisted of 5,000 guardsmen. Assuming that pretty much the whole regiment is made up of Guard infantry squads (being the quintessential building block of the Imperial Guard), 80% of them were given lasguns, leaving 20% with other weapons. Half of these other weapons are heavy weapons (heavy stubbers, heavy bolters, mortars, lascannons, or autocannons) and the other half are special weapons (grenade launchers, flamers, plasma guns, melta guns). This means there are some 500 heavy support weapons in our example infantry regiment. Let's add in the shipping cost of these heavy weapons to our previous article.
Ammo consumption per year of campaigning:
4k Small Arms 500 Heavy Weapons Combined TEU*
Regiment w/Lasguns & 8.25mm stubbers 5,760 kg 813,037 kg 818,797 kg ~40
Regiment w/Lasguns & .50 stubbers 5,760 kg 2,080,500 kg 2,086,260 kg ~104
Regiment w/Lasguns & h. bolters 5,760 kg 6,205,000 kg 6,210,760 kg ~310
Regiment w/Lasguns & 8.25mm stubbers 224,560 kg 813,037 kg 1,037,597 kg ~52
Regiment w/Autoguns & .50 stubbers 224,560 kg 2,080,500 kg 2,305,060 kg ~115
Regiment w/Autoguns & h. bolters 224,560 kg 6,205,000 kg 6,429,560 kg ~321
Regiment w/Lasguns & 8.25mm stubbers 1,872,000 kg 813,037 kg 2,685,037 kg ~134
Regiment w/Boltguns & .50 stubbers 1,872,000 kg 2,080,500 kg 3,952,500 kg ~198
Regiment w/Boltguns & h. bolters 1,872,000 kg 6,205,000 kg 8,077,000 kg ~404
TEU: Twenty-Foot Equivalent, or one standard twenty-foot shipping container (max weight load: 20,000kg)
The shipping cost to equip every squad of guardsmen with even a single heavy bolter is immense. A hypothetical regiment with lasguns and heavy bolters needs triple the logistical capacity of a similar regiment using only heavy stubbers. It is no wonder that lighter regiments from poorer worlds, like the Tanith, end up with heavy stubbers--despite being the inferior weapon, they are much easier to supply. As for the Death Korps, reducing the number of high-cost weapons such as heavy bolters by fielding supplemental heavy stubbers (even twin-linked heavy stubbers) reduces supply needs. This grants an edge in the kind of industrial attrition-based warfare that they specialize in. Such wars are won not through superior force, but superior economy of force. Gang, cult, and renegade forces obviously use heavy stubbers because, lacking the resources of the Imperium, they have to use what's available to them.
This time, I'm not going to multiply these numbers by one billion to determine the shipping costs for the entire Imperial Guard (est. 5 trillion troopers), because the numbers would be increasingly misleading. Unlike with lasguns, we can't make a reasonable assumption about which mix of heavy weapons (heavy stubbers, heavy bolters, missile launchers, mortars, autocannons) are used across the guard, as most regiments seem to field a mix of weapon types. Even our 5,000-guardsman example regiment above is deeply misleading, as 100% of their heavy weapons wouldn't be the extremely ammo-hungry heavy bolter or even the still-very-ammo-hungry heavy stubber.
Other Takeaways
Each heavy bolter has a 34kg 'day of supply,' meaning that it is expected to use that weight of ammo per day on average. This is an outrageously heavy load for a single trooper (and still pretty miserable for two troopers in a heavy weapons team, before factoring in the weight of the gun itself), so is presumably distributed among the squad. Each trooper in a 10-man squad would have to handle an annoying-but-doable 3.4kg of heavy weapons ammo if their unit were assigned a heavy bolter, or a svelte 1.1 kg with a heavy stubber. I know which of the two that /r/ultralight would pick! edit: I grossly misunderestimated the degree to which militaries do not care about knee problems later in life. Expecting those heavy weapon troopers lug around 34kg of ammo wouldn't make the Guard blink.
It's no wonder that the default turret weapon of a chimera is the multilaser. Assuming the multilaser's battery is recharged by the transport's own engine, each multilaser turret saves 12,410 kg of interstellar shipping per year. Heavy bolter turrets seem almost wasteful by comparison! Do your part: avoid waste by switching to multilasers! pewpewpew!
Looking at the immense interstellar shipping needs of 500 heavy weapons per regiment, I think my estimates of one per squad may have been too high. Perhaps only very well-equipped, well-supplied regiments field a heavy weapon in every squad, while most get by with just a single heavy weapon squad of 3 per platoon of 50, or even fewer. This would reduce heavy weapon ammo useage by 2/5ths (and increase small arms ammo consumption slightly, with one more rifleman per squad). This continues to reinforce the point of the last post, however: the more shipping space that can be saved by switching to lasguns, the better! The Guard's other weapons are incredibly hungry for ammunition. Using a mix of other weapons, like lascannons (which have rechargeable power cells like lasguns) would reduce ammo useage, but the overall number is stlil unexpectedly high. This begs the question of why the Guard doesn't issue its infantry multilasers, which are roughly equivalent to heavy bolters (in most editions, they were the same points cost and had similar use cases) but without the ammo consumption. Perhaps multilasers have impractically large power cell requirements, even compared to lascannons, to be man-portable?
There's also the obvious question of the weight of the firearm itself: heavy bolters are clearly larger, and thus heavier, than heavy stubbers. It's no surprise that both the Death Korps and most of the old pewter range used wheeled weapon carriages for heavy bolters, while heavy stubbers are man-portable. The heavy bolter is nicknamed the 'back breaker' for a reason.
Here's a thought experiment: if the Munitorum wrote the rules of 40k, then a model's points cost would be derived from its logistical materiel demands. If we set 1 point to be equal to a single lasgun's annual interstellar shipping requirements, then an autogun would cost 39pts, a boltgun 325pts, a heavy stubber would be apocalypse-only at 2,889pts, and a heavy bolter would be a bespoke Forgeworld weapon at 8,618pts, replete with its own certificate of authenticity and shipped in a velvet-lined box. Throne help you when "that guy" at the club shows up with a Punisher cannon.
/u/RaymondLuxury-Yacht's discovery of the 8.25mm heavy stubber, which is explicitly what infantry renegades and heretics are equipped with (and, presumably, Death Korps infantry) has pretty sweeping logistical implications. This calibre is much closer to the modern 7.62mm used in the very common M60 machine gun, which is issued to soldiers today who are expected to keep up (more or less) with riflemen in their unit. The M60 is considered a crew-served weapon (it is usually operated by a team of two or three), but is potentially manageable by a single soldier (if they have help carrying ammunition). This neatly explains the Tanith First's use of crew-served heavy stubbers with the Death Korps' and cultist's practice of equipping a single soldier with one. (We might assume that at least one other member of the squad is carrying extra ammo for the heavy weapon trooper.) An infantry squad with lasguns and an 8.25mm heavy stubber now has 1/10th the ammunition shipping requirements of a theoretical infantry squad wielding boltguns and heavy bolters.
I'm planning future posts that talk a little more about the PDF and cultists/renegades, as well as one that goes into some of the other heavy and special weapons issued to the Guard.
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