Stubbers, or stub guns, are weapons from as early as the halfway point of M2, but mostly 20th century guns (our times) in the 41st millennium. Needless to say, most haven't aged very well when you consider how powerful everything else is. The only thing that they have going for them is they are cheap, they can still kill an unarmored humanoid target, and are durable as hell and depending on its mechanics and care, given can be and have been in use SINCE M2. Sadly, they are incredibly weak against much of the universe's serious threats - in fact, they are among the few things that a Guardsman's flak armor will reliably stop a direct hit of. This should give you an indication of exactly how weak they are. Of course, anything above it is guaranteed to fuck up your Guardsman and Space Marines quite well, and stub guns are actually capable of downing Terminators if you aim for the joints, lenses, or other sensitive equipment (read: if the unlucky marine rolls a 1). Just because a gun is simple doesn't mean it's not effective, especially when it's scaled up a few (dozen) calibers. But just remember - every dog has their day. Especially as the latest Primaris armoured units have found fresh use for them.
- 1 Disambiguation
- 2 Primitive Variants
- 3 Ancient Variants
- 4 Modern Variants
- 5 Advance Variants
- 6 Gallery
One of the pitfalls of Games Workshop is that they really don't have an internal canon police. To wit, the difference between Stub weapons and Auto weapons is rather blurry. Some authors write as though these technologies are one-and-the-same, citing only vernacular differences for the existence of multiple terms for ignited-gas slug-throwers (or sometimes totally writing out one term or the other!). The game itself is not an exemption, as edition-to-edition, codex-to-codex, and supplement-to-official author changes cause a mess of personal opinion writing over personal opinion, and some authors sling both terms with abandon, interchanging one for the other whenever they feel one term is becoming overused.
To clarify, it is generally agreed that there are both Stubbers and Auto-weapons. Stub technology tends to be lower-tech, revolvers-to-WWII style weaponry, with an air towards larger-caliber and higher stopping-power. Auto-weapons tend to be higher-tech, Cold-War-and-on style weaponry, which emphasize accuracy and fire rate. It's been suggested that any full scale cannons would be classified as Auto-weapons, however calling a battle cannon or macro cannon an Auto-weapon is a bit of a stretch. Bigger caliber and relatively slow rates of fire denote Stub weapons, until you hit the point where infantry can no longer wield them. Anything with explosive, tracer, frangible, or incendiary rounds are typically Auto-weapons. Muzzle-loaders like muskets or arquebuses are neither Auto nor Stub. Furthermore, autoguns are generally (but not always) described as firing caseless ammunition and also include such types of weapons as gauss rifles (the electromagnetic kind not Necron bullshit) and even gravitic propelled slugs.
A good example to use would be pistols: A stub pistol would be either a revolver or a semi-auto magazine-fed pistol, while an autopistol would be either a handheld automatic pistol or a burst-fire pistol. It could also be something along the lines of an Uzi, MAC-10 or any other SMG whose magazine is located in the grip, judging by the illustration of an autopistol given in the Imperial Infantryman's Uplifting Primer. High-tech, Shadowrun-esque revolvers are still Stub weapons, while Krieg-made automatic slug-throwing cannons are still Auto weapons by default, and hand-crank Gatling guns could go either way. Pepperbox-style breach-loaders would be neither, and futuristic ignited-gas projectile weapons are Auto weapons. Since GW is pathologically incapable of consistency, the Cult Mechanicus Tech-Priest Dominus carries a 5-shot burst pistol called a macrostubber, even though its form factor and performance place it in the 'autogun' family. Though it likely probably fires similar rounds to a heavy stubber, they only match in power not caliber, and it is the method of the weapon system’s function which distinguishes the type of weapon.
For further comparison between Stubbers and Autoguns, click here.
Wooo boy. If you want to role play as a 16th century Pirate, then the Flintlock Pistol is for you. These simple black powder weapons can take many forms, from finely crafted pistols constructed for the nobles of low-tech worlds to simple pipe and powder affairs used by underhive scum. They are uncommon and are famous for their low battle characteristics but those which do exist are sometimes very heavily ornamented and carried by high ranking officers mainly as decoration.
Of course, whilst you may scoff at the idea of going into a battle filled with tanks and space ships with an 18th century gun, do take note that the more master-crafted versions could be quite deceptively deadly by virtue of incorporating some form of advanced tech into, seemingly, primitive and "backward" design. For example, such constructs could be capable of holding plasma munitions that can crack open power armor in a single shot. So while actually using a black powder pistol (in all but the most retardedly desperate situations) will get you in trouble, you never know if some dude has an archaeotech pistol that resembles one just to look cool. Laugh at your own peril.
Muskets are primitive firearms, utilizing explosive powder and a crude firing mechanism to propel a lead ball. Like the Flintlock Pistol, these crude devices can only fire once before reloading and are prone to failure. Slow, inaccurate, and unreliable, they are only made and used on backwards planets. However, they are extremely easy to construct and maintain even from scrap-parts and with an absolute minimum of skill and knowledge about firearms operation. For this reason they are known to be quite popular among outlaw members of Hive societies such as the Ratskins and Scalies of the Necromundan underhive. The Planetary Defense Forces of Feral and Feudal Worlds also sometimes make use of muskets.
Like the Flintlock Pistols, master-crafted Muskets could be quite deceptively deadly by virtue of incorporating some form of advanced tech into, seemingly, primitive and "backward" design. That “backward” musket could hide archaeotech capable of making a Thermal Cannon look like a firecracker.
A primitive shotgun. Also known as a Scatter Gun, the Blunderbuss is an exceedingly simple weapon made out of one or more short barrels strapped to a solid stock. An explosive charge is primed at the bottom of each barrel, then a large amount of metal fragments, stones, pieces of bone or anything else likely to cause harm are packed in on top.
When the weapon is discharged, it belches out this "ammunition" in a vast swath which will hopefully find itself somewhere in the locale of its intended target.
Outside of primitive societies, such a crude, ineffective and dangerous (to its operator) weapon is only used by the poorest or most desperate members of society. Usually it can be found in use by criminal gangs, for instance the Ratskin Renegades and Scavvies of Necromunda's underhive. Gretchen also craft these weapons, even upsizing them for their primative dreadnoughts.
A primitive weapon found on Necromunda and used exclusively by the Scalies. Basically a 18th century cannon with a trigger attached to it. A scatter cannon is simply an enlarged version of a Blunderbuss or scatter gun with a heavy barrel and a fist sized bore. The greater weight of the shrapnel and explosive charge used in a scatter cannon increase its range and make it a lot deadlier in the confined conditions of the underhive.
If all else fails, the Scalie can basically just use the giant cannon as a giant makeshift club. Any poor scrub would get crushed by the weapon's immense weight. The Scatter Cannon is sturdy enough due to be constructed mainly with one piece of reinforced wooden log and one piece of a steel firing bore. Thus, the Scatter Cannon is essentially the watered down version of the Ogryn's Ripper Guns.
Scalies are the only underhive denizens with the massive strength to take the recoil from these powerful primitive weapons.
God made men, Sam Colt made them equal, and John Browning made them civilized. It's a basic pistol in two variants: the stub automatic which is like a .45 caliber handgun and the stub revolver which is, of course, a generic revolver, more of which can be explained below. If you're in a gang on a hive world, it'll work pretty well because you're probably going to be shooting at other people without armor, or lightly armored local law enforcement. Very reliable, unlikely to jam, manufacture is a breeze, and ammo is plentiful. However, if you're trying to shoot an Ork, even headshots might just bounce off his skull. Though, the same could be said of autoguns and lasguns, minus the actual bouncing of course.
The stub revolver carries fewer rounds than most pistols but is very reliable and easy to operate. As bullets can be inserted individually, it is relatively easy to load in specialized rounds when needed. It is one of the most ancient of pistol designs and serves as an ideal backup weapon.
Unlike the Stub revolver, this pistol weapon fires in semi-automatic. Like the Autopistol it is easy to produce and maintain, but less accurate at longer ranges. Just as common as the revolver variant, the stub automatic is relatively less reliable, but allows for a greater rate of fire and magazine capacity.
Stub Revolver, looking much like The Spy’s revolver
Stub Automatic, one must wonder how any magazine is supposed to fit inside such a grip (Uses a cylinder clip at the front.)
Basically a semi-auto stub pistol on steroids, not unlike real-world .50 cal Desert Eagle or .454 Casull pistols in operation (It is worth noting that at least one model of hand cannon has its caliber listed as being .54 cal, that equals roughly 13.06mm).
Hand cannons are almost invariably heavy and cumbersome by pistol-grade weapons standards, in addition to having unforgiving recoil, requiring a degree of training and physical resilience to wield such a firearm.
However, hand cannon do reward their users with the ability to kill even armoured or resilient to damage opponents (like Ogryns, Orks and Necrons). Sort of. They are still closer in power to stub pistols than bolt pistols for instance. But they are far easier to produce meaning Guardsmen, typically Sergeants and vets, could use them as a surprisingly powerful backup weapon. And if you find yourself up close and personal with an Ork, Necron or Genestealer, you will want as much firepower as you can get your hands on.
Its big brother is called the Stub Cannon which can be read below.
The Sawn-Off Shotgun is a catch-all term to describe any shotgun that has its barrel...well...sawn off. This is one of the most ancient of weapon modifications. The affects of which decreases the range, whilst increasing both the spread and ease of handling.
By sawing off the barrels, the shotguns turns from a rifle into a pistol. So you essentially have a shotgun pistol for all intents and purposes. Due to such unsanctioned modifications, they are not widely popular in the Imperial Guard. Instead, they are used by hive gangers where Imperial oversight is non-existent.
In the Necromunda tabletop, the Sawn-Off is easily one of the worst weapons in the game. It has worse range than a Pistol and its attributes is easily overshadowed by other short-range weapons like the Flamer, Melta or you know, an actual Shotgun. There is no situation where taking this weapon is better than a pistol. Avoid it.
Often called "stub-blasters" or more simply "stubbies", the Stub Cannon is an especially large version of the hand cannon that fires massive, high-caliber rounds so massive that the recoil can break bones -- basically like a Torgue pistol from Borderlands 3. As such, most gangers in the underhive could barely lift such a weapon, let alone take the grievous recoil from firing one in the first place. Due to their unnatural and inhumanly large muscle mass and bulk, they're favored mainly by the members of House Goliath.
Like the Catachan's and their Knives, carrying such a gun is more a show of strength (and a dick measuring contest) than it is a practical weapon, but that just adds to the appeal for your average Goliath ganger.
The Stub Cannon looks like an enlarged Stub-Revolver. How quaint.
The gun that coins the term Stubber.
No, really, take a Mosin or a Springfield and you got one of these. Shit's built to last.
Generally, a simple medium/high-caliber bolt-action or semi-auto rifle. Also called the Stubber. It is basically your typical, everyday hunting rifle you can buy today with some slight modifications. Existing in many patterns, generally such a rifle is regarded as a lowly civilian-grade weapon or tool.
However, it often sees action not as just a hunting or farming tool, but as a combat weapon in the hands of lowly insurgents, cultists, or militia fighters. It's likely that high powered Stub Rifles could also be seen to use the same or similar rounds to a Heavy Stubber, minus the automatic fire. Heck, some high powered Stubbers could become a makeshift Sniper Rifle. Typically a Stub Rifle acts as a Marksman Rifle in these cases. Its rule 63 equivalents are the Las-lock or Autogun. Don't look down on the stub rifle, some of the most powerful weapons in the galaxy are stub weapons.
The primary sidearm of the triple gunslinging space cowboy of the Kelermorph Hybrid. From an initial perspective, these Stub Revolvers look like any other form of Stub Revolver. But don't let that fool you, for these revolvers pack enough of a punch to make a Hand Cannon and even a Bolt Pistol look like a pathetic Flintlock Pistol in comparison.
For you see, the bullets of a Liberator Autostub is made from extremely 'rare' depleted volonium shells. Rare is in quotations because they are made by disgruntled workers from any normal arms factory, produced by the stuff being smuggled out in trace amounts. Which begs the question on why the Imperium never seem to make bullets out of this volonium stuff if god damned sweatshop workers can smuggle them out and make it by themselves. (Maybe genestealers shit out volonium?) The fluff suggests that the normal Imperium does not use them because making these things is a deadly task since you're likely to be exposed to high levels of radiation (which suggests that to make depleted Volonium they first have to synthesis normal Volonium which, before you ask, is not a real element). But since when have the human costs of production stopped the Imperium "grim dark is our catchphrase" of Man? And it's deadly only to those aforementioned sweatshop workers because their basement armory has zero radiation protection, unlike a sanctioned worker specialized in that task. Anyway, these bullets are supposedly hard enough to pierce Power Armour and the hulls of light tanks (which makes no sense anyway because it still wouldn't have the kinetic energy to defeat said armor anyway), but crunch-wise they're only -1; not too bad, given the rate of fire, yet not quite "turn a tank inside out" good,
which may also explain why the Normal Imperium doesn't field them crunch in this case is dramatically different from fluff in which these bullets are easily tank and Marine killers. They've got better (and cheaper, and probably wayyyyyy less radioactively lethal) shit to produce AP rounds with (and yet nobody, even Space Marines, ever gets any of these hypothetical AP rounds?).
On tabletop, these are the Kelermorph's rootin' tootin' shootin' S4 AP-1 2 damage Pistol 2. The Kelermorph has three of these babies and can just gun down space marines and below with ease. Cypher wishes he could get guns this good.
Imperial shotguns, in fact, changed little over millenia - they are the same smoothbore firearms, principally designed to either fire buckshot at close ranges or slugs to engage targets up to medium ranges. About the only big change that the Imperium employs to the gun itself is putting the gun's tubes in a metal box. These are generally simple and cheap in construction and exists in different patterns and models throughout the Imperium of Man. They range from archaic over-and-under shotguns and pump-action ones to the full auto combat shotguns, employed as a signature weapons of Adeptus Arbites, to models specifically tailored for Space Marine's biology, and thus having great mass and recoil, but also vastly greater stopping power.
Also worth noting is that along with simple buckshot or slug shells, Imperial shotguns can also fire specialised rounds, usually produced by the Adeptus Mechanicus, including the dreaded Executioner-pattern sniper slugs, having the ability to change their trajectory mid-flight and home in on their target thanks to their miniature on-board cogitator. The Deathwatch also maintains unique shotguns with specialized alien-killing rounds, utilizing armour-piercing solid rounds, flame-belching shells, or rounds that fill the room with deadly bouncing ball-bearings.
Longrifles or Long Rifles are a catch-all term for any Stubber carbine/rifles. They should not be confused with the Eldar Ranger Long Rifle as these two weapons are on a completely different spectrum. They're ironically modeled as being pump action and, while this is technically feasible, it is rather impractical due to pump-action weapons being inherently more inaccurate than other forms of weapon (the action of pumping the gun tends to throw off one's aim).
They have a longer range than a Stubber by sheer fact of having better materials and a higher tech-tree. They could also hold a lot more ammunition and could, theoretically (Depending on the design) have variable fire rates.
On the Necromunda tabletop, they are capable of reaching out across the entire battlefield, and more accurate beyond 24”, the long rifle is perfect for taking out targets with precision. Strength 4 makes this weapon deadly, and pairing that with the Knockback trait makes them devastating.
The Ogryn Ripper Gun is a large, brutal, and simple weapon designed for use by Imperial Guard Ogryns. It is a heavy automatic shotgun, built as simply and solidly as possible in order to survive being used by the Ogryns who use it as much as a club as a firearm. Think of it as the high-tech grandson of the Scatter Cannon. It can fire either a heavy shell or a hail of shot. By design, the Ripper Gun does not have a long range to better fit the Ogryns' instincts for close combat, and many also have a fire rate limiter to prevent them from firing off an entire magazine's worth of ammunition at once.
Ripper Guns are intended to be fired to soften up the enemy before the Ogryns charge into close combat, and are built particularly robustly so that they can stand up to the Ogryns' use of them as clubs in melee. Ripper Guns can also be fitted with Ripper Saws. A Ripper Saw is, as the name implies, a saw blade that is attached to the end of a Ripper Gun which is intended to provide the Ogryn with an effective close combat melee weapon once they close with the enemy. The Ripper Gun is one of the few Imperial weapons that is intentionally crafted for use by Ogryns, and its design is intended to be much more durable and larger than a standard Imperial weapon, to compensate for the Ogryns' size, extreme clumsiness, and intellectual deficits.
Well-known is the Heavy Stubber, a machine gun used as a vehicle mount in the Imperial Guard, because in 40,000+ years, humanity has still been unable to top the genius of Weaponsmith John Browning's legendary M2 (who's surprised?). Just ask the goddamned Orks.
It is basically a
direct equivalent of the Browning M2 .50 cal Heavy Machine Gun (except for the Vraks-pattern, which looks more like a M1919A6 and some that look like MG42's). The Imperial Guard uses them in the same way as light machineguns were in WW2 and a SAW would be used today. Various models on tabletop visually run from .50 to bolter sized bullets to rounds that probably are larger than a heavy bolter’s hanging off a short chain. So, who the fuck knows. They all hit the same anyway. Unlike the smaller Stub guns, Heavy Stubbers actually contain enough mass to do similar damage to a Bolter round at a much higher rate, (albeit with more recoil) and will reliably blow people's limbs off now as easy as they did then. Unlike the others which have been phased out, these are still in the mainline army arsenals, and are often pintle-mounted on vehicles or used in Heavy Weapon Squads in the Imperial Guard, especially for vehicles produced from worlds that do not have the resources to produce Heavy Bolters, or those who just find it more economical to push out a hundred Heavy Stubbers with the man-hours it would take to make a single Heavy Bolter and rounds for it. Obviously, they are not as strong as the Heavy Bolter they replace, which is several times more powerful than a regular Bolter, but they are still damned powerful enough, and they DO GET SHIT DONE. Besides, if you're just trying to gun down enemy infantry, you don't strictly need a Heavy Bolter, or even a Storm Bolter, when a Heavy Stubber is just as capable of turning a human or human-equivalent into so much jelly. A heavy bolter is nice for ruining their cover if it were used in real life, so everyone else can have a merry time slaughtering the exposed enemy. Then there are the different types of ammo, such as ones that break apart in the target and the pieces explode. A similar but heavier laser version of this weapon would be a multilaser.
Note that despite our metaphorical praise calling it the M2 .50 cal of the future (for its simplicity and dependability), its actual calibre according to Imperial Armour books is an "8.25 long" cartridge. Assuming this means "8.25mm diameter, rifle cartridge" this puts it at a "mere" 0.325, not 0.50(which would be 12.7mm). In fairness that was only the calibre of the Vraks pattern mentioned above, which was modeled after the smaller MG42, which fired the 7.92×57mm cartridge.
Alternatively it could be an 8.25cm long cartridge. Remember that most cartridge specifications come with both the nominal diameter and the case length- .50 BMG is also known as 12.7x99mm, for example. The heavy stubber would thus be something like 12.7x83mm. With fancy futuristic propellants, maybe they figured out a way to cram more energy into a shorter case. Who knows?
Surprisingly, an enhanced heavy Stubber called the Ironhail Heavy Stubber is one of the many weapons used by the Primaris Marines' transport, the Repulsor Tank, and is also present on a fair number of AdMech vehicles.
Why it uses a heavy stubber instead of the much more potent and commonly used heavy bolter is a mystery for the ages. Again, reliability and ammo simplicity. No fancy rockets, just bigass bullets of doom. Also although it has no impact in-game heavy stubbers probably have much more ammo capacity and faster, more accurate rounds, being smaller and lighter and relying on pure impact (thus speed) to inflict damage compared to a heavy bolter round. Google the .50 SLAP round for a potential real life equivalent. There is also the Icarus variant designed for AA work, frequently twinned.
The Death Guard also make use of a variant known as the Heavy Slugger, which fires Heavy Bolter level shots at a faster rate.
While the Imperial sniper rifles are generally a rather broad class of weapons including, for example, the Long-las sniper lasguns used by the Imperial Guard, at least some of the sniper rifles utlized in the Imperium are actually solid-slug ballistic weaponry, firing high-caliber, powerful rounds to achieve maximum range and precision with their shots. Some specialist snipers like to add in specialized rounds in their Sniper Rifle for the 'special occasions'.
Space Marine Chapters, particularly Scouts, utilize a unique model of Sniper Rifle. A Space Marine-pattern Sniper Rifle fires a solid shell and boasts powerful telescopic sights that allows the wielder to fire at enemy weak points and distant foes with extreme accuracy.
The Exitus Rifle's kid cousin. The Exitus Pistol is an Imperial pistol and a signature weapon of the Vindicare Temple of the Officio Assassinorum. Like its cousin the Exitus Rifle, it is a masterpiece of Adeptus Mechanicus engineering and is custom-built for the requirements of the individual assassin. The Pistol is largely a backup weapon for the Exitus Rifle and is used in the rare circumstances the assassin is discovered, cornered, or in need of rapid-fire weaponry. With a built-in silencer and the capacity to load and fire the same specialized ammo as its big brother, it has saved the lives of many Vindicare Assassins.
Like its rifle counterpart, the Exitus Pistol is capable of firing a variety of specialized ammunition. These include:
- Shield-Breaker Rounds - Overload the personal Force Fields of the target
- Turbo-Penetrator Rounds - Use a two-stage charge to punch a secondary round through the thickest armor.
- Hellfire Rounds - Contain virulent bio-acidic toxins that can reduce targets to ash.
Arguably the most iconic (and dreaded) of such Imperial "solid-slug" sniper rifles are the Exitus rifles, employed by field agents of the Officio Assassinorum's Vindicare temple. Each of these rifles is a one-of-a-kind "work of art" which is painstakingly hand-crafted by Adeptus Mechanicus artisans to match the particular specs of each individual assassin. Its exceptional range and power also imply that the rifle uses something far more advanced than mere chemical gunpowder combustion to accelerate its bullets (however, the exact mechanics of its action is highly classified by Adeptus Mechanicus top brass). With such high velocity, combined with specially made "turbo-penetrator" rounds, designed to make quick work of any armor including such utilised by super-heavy tanks and TITANS (in the glorious days of 5th edition GK codex, that baby rolled 4d6 for armor penetration), the Exitus rifle gives the Vindicare assassin a chance to slay practically every conceivable target in just one well placed shot...
The Exitus Rifle is capable of firing a variety of ammunition depending on the target. These include:
- Shield-Breaker Rounds - Overload the personal Force Fields of the target
- Turbo-Penetrator Rounds - Use a two-stage charge to punch a secondary round through the thickest armor.
- Hellfire Rounds - Contain virulent bio-acidic toxins that can reduce targets to powder.
- Immolator Rounds - Rounds that caused most soft targets to violently explode at the molecular level leaving behind nothing but ash. These are the Rounds most often used in conventional sniper operations.
The Macrostubber is the Mechanicum's more advanced and powerful variation of a typical solid-slug ballistic weapon (As expected from the AdMech). The standout feature of the Macrostubber is just *how fast* it fires, especially considering it's basically an SMG with similar power to a bolter, or Ork shoota. This type of antique weapon is used by Adeptus Mechanicus Tech-Priests, and is able to hurl out a thunderous cloud of specially designed bullets (the exact method of accelerating its projectiles is not disclosed by the Techpriests, however the looks imply something more than just gunpowder is involved). A Macrostubber can apparently fire at a rate exceeding the Heavy Stubber, a bloody MG, by a ratio of 5:3! Maybe it's just an MG 42 cut down to pistol form? It's further possible that Macrostubbers are coilguns or railguns, which would explain the need for "specifically designed" (read: ferromagnetic) projectiles. Maybe the electromagnetic firing mechanism removes the need for moving parts, accelerating the rate of fire by removing the need to cycle a bolt? Perhaps it's only as good as a normal autogun, but the Magos that wield them can think so fast that they aim and fire with absolute precision and accuracy, making literally every shot count.
You know what, just think of it as a drum-fed, compact, heavy machine gun with a crazy-fast rate of fire, and you won't go insane. Or maybe you will considering it's practically a .50 cal machine gun that fires almost as fast as an Assault Cannon, and is wielded as a pistol! In theory could be dual-wielded, or more if you have extra robot arms...
This weapon has proven quite skubby in /tg/, due to the fact that some people have taken to calling it an Autogun due to its technological superiority and rate of fire despite the name. Then again, some may have pointed out that it could be just a more portable and lightweight variant of the Heavy Stubber. As noted in the Disambiguation section and throughout the article, the fluff doesn't do a good job of drawing any consistent lines between Stubbers and Auto-weaponry.
Also worthy of note is that stubber and autogun refer to the mechanism of the weapon itself, whereas a bolter specifies both the weapon, and the special explosive
rocket-assisted rocket-propelled (assisted just gets it up to the right muzzle velocity, propelled does far more) munition it uses. It could very well be that a macrostubber employs the simple and reliable mechanics of a stubber to fire a low-velocity high-mass (hence, low initial recoil) rocket-assisted round. Historically, rocket firearms have not proven too reliable, but the biggest problem is the ammunition; it would make perfect sense that these weapons function only if maintained and used by a member of the AdMech.
Another AdMech weapon exclusive to the Skitarii (and, of all people, the Cultist Champion from the Blackstone Fortress game). The stubcarbine, though small, has the stopping power of the heavy stubbers mounted on the vehicles of the Imperial Guard. When a squad of Sicarian Infiltrators opens fire with these weapons, the air fills with an avalanche of solid shot that chews their victims to shreds. It can be assumed to have a shorter range to compensate for their high rate of fire or because of it's short barrel and high caliber. It's rate of fire and high power beg the question: How long does that tiny magazine last? It most likely has small magazine capacity in the form of a barrel/drum magazine to squeeze out more room and is probably capable of being used as “bang you're dead” with quick single shots at different targets or blowing its load at one or a tight group of targets rapidly. With a squad equipped with these, the enemy will be dead by the time you need to reload, so magazine size won’t really matter, and if not, Skitarii are incredibly expendable to the AdMech anyway. Plus, as cyborgs, it's not inconceivable that an Infiltrator can reload extremely quickly. The intention could be that an Infiltrator can rake a group of enemies with fire, then run a reloading macro while doing something else, like charging into close combat or taking cover.
Judging from how they are described in fluff, Stubcarbines seem to be a lightened variant of Heavy Stubbers, outfitted with some kind of recoil suppression system which allows them to be fired as handheld weapons by the Skitarii, albeit with shorter range due to sporting a much shorter barrel than the actual Heavy Stubber. It seems like the thinking was "a carbine is a lighter version of a rifle, so a Stubcarbine is a lighter version of a Heavy Stubber." This would make it an... assault rifle? High caliber (but otherwise normal) carbine? Uncertain, go ask /k/. (/k/ here, sounds like the Heavy Stubber "variant" was not a .50 but a 7.62x51 or equivalent, which would make it a medium machine gun. But knowing the Admech, it's not improbable that it is a .50 in which case it would be a compact heavy machine gun, or a high caliber SMG, depending on the overall power of the rounds)