Combi-weapon
"You know what would be better than a gun? Two guns!"
- – Basic American
Combi-weapons are specialized weapons in Warhammer 40,000, mainly used by the Imperium of Man, Leagues of Votann, Chaos Space Marines, and the Orks. A combi-weapon is essentially a bolter with another weapon integrated into it. Among the Space Marines, they're commonly used by Terminators and most famously by the Deathwatch. Since 8th Edition came and turned combi-weapons into a flat-out upgrade, individuals armed with them can either shoot any of the two or - and this is something new compared to previous editions - shoot both at the same time at the cost of a shooting penalty. They come in several varieties.
Space Marines/Imperials[edit]
Generally speaking, despite obvious foreknowledge of underbarrel grenade launchers and other such equipment, combi-weapons in the modern sense were first developed during the Great Crusade in an effort to improve the firepower of Astartes wearing Terminator armour because a single Bolter was just not enough. So the Adeptus Mechanicus started by simply slapping two Bolters together, creating the Combi-Bolter and it snowballed from there. Those weapons were just awesome enough that their use spread from Terminator units to the entirety of the Space Marine Legions and beyond. The Combi-Bolter was later upgraded further to the purpose-built Storm Bolter (while the traitors got stuck with the older variant), but the other combi-weapons remain much the same as they were back then, combining the 'take-all-comers' flexibility of a good Bolter with the extra punch of a secondary weapon.
Combi-weapons involving bolters tend to get a bit confusing and weirdly designed, while usually they are the sensible under-slung attachment, some just go with the bolter itself being the underside weapon, the weapon attached to the topside instead or alternatively just welded to the side. So basically you can have a full-auto explosive gyrojet machine gun with an under-slung attachment or have said explosive gyrojet machine gun be the under-slung weapon. Shockingly, the only weapon attachment that is usually under the bolter is the grenade launcher, who would have thunk it?
Magna-Needle Mk.X Pattern Pistol[edit]
The Magna-Needle Mk.X Pattern Pistol or simply known as the Magna-Needle is a type of non-military combi-weapon used by the Primes of House Van Saar on Necromunda.
These weapons are basically an inferior version of a basic Combi-Melta, as instead of a Bolter, the Magna-Needle uses a Laspistol instead. Yes, it is a Meltagun crossed with an under-barrelled Laspistol. Not sure why it has the word 'needle' in it as that would denote a completely different weapon family. Nevertheless, the combo surprisingly works, or at least, works better than the Ultra-Needle Mk.IX Pattern Pistol (We will get to that later), since the short-range of the Melta is offset by the long-range and relatively accurate and reliable Laspistol.
On the Necromunda tabletop, unfortunately, it kind of fucking sucks. They are just barely cheaper than the actual special weapons. The Laspistol just does not complement with the punishing combi rules as you have to roll the ammo check twice and succeed on both in order to pass a result. Meaning you are most likely going to fail your hits than anything else.
Ultra-Needle Mk.IX Pattern Pistol[edit]
Another combi-weapon used by the Primes of House Van Saar on Necromunda is called the Ultra-Needle Mk.IX Pattern Pistol.
Remember the jokes and memes on how the Lasgun can be used as a laser attachment for more useful weapons? Yeah, the Ultra-Needle Mk.IX Pattern Pistol is basically that in reality. Unlike say, the Magna-Needle where it can at least excuse the existence of the Laspistol by pairing it with the incredibly short-ranged Meltagun, the Ultra-Needle Mk.IX Pattern Pistol has no such excuses. Nothing more than a Plasma Pistol duct taped on top of a Laspistol. The sheer firepower difference between the two literally makes the Laspistol to be as useful as a laser pointer. Again, like the Magna-Needle, we aren't sure why this Plasma-Laspistol hybrid has the word 'needle' in it.
On the Necromunda tabletop, the fluff kind of matches the crunch as it fucking sucks. They are just barely cheaper than the actual special weapons. The Laspistol just does not complement with the punishing combi rules as you have to roll the ammo check twice and succeed on both in order to pass a result. Meaning you are most likely going to fail your hits than anything else.
Stub Gun-Plasma Combi-Pistol[edit]
A combi-weapon used by the Forge Tyrants of House Goliath on Necromunda.
If you thought the Laspistol attachment has suffered a more unnecessary existence under the Ultra-Needle Mk.IX Pattern Pistol, wait till you see the fate of the poor Stub Gun used by this Goliath combi-weapon. And no, it is not a Stub Cannon you are looking at; the Combi-Pistol seriously uses an under-barrelled revolver underneath a Plasma Pistol. At least the Laspistol has the excuse of accuracy and having a large ammo pool of around 50 shots; the Stub Gun, however? Fucker barely could house six rounds of pea shooter grade firepower before needing to reload. And you can forget about accuracy since this is House Goliath we are talking about.
Funnily enough, in contrast to the ones used by Van Saar, on the Necromunda tabletop, the Combi-Pistol is a surprisingly more cost-effective weapon. But that is largely because it is the cheapest plasma weapon for House Goliath. The Stub Gun is just there for window dressing.
Combi-Flamer[edit]
A Celestian's erotic fantasy boltgun with a flamer attached to it. When you want both the firepower and armor-cracking effects of the Bolter but also want to have the horde-cleansing capability of the trusted Flamer, accept no substitutes. Especially useful for close combat situations or assaulting a genestealer hive to save your surrogate daughter. Combi-flamers are one of the most common and most well-liked type of combi-weapon, the other being the combi-plasma, due to its versatility.
Like all Combi-Weapons in 8th edition, you can fire either/or as per normal, or shoot both at a -1 penalty. Because of its Flamer attachment, you can now autohit all enemies and defend your dudes when they are being charged.
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Deathwatch -
Cassius's -
Legion -
Sternguard Issue -
Blood Angels Sternguard -
Cataphractii Terminator wielding a Combi-Flamer with Chainblade attachment
Combi-Melta[edit]
A bolter with a meltagun attached to it. As you can imagine, these are used when there is a large presence of enemy armor. Combi-meltas are favored by tank-hunter specialists who like the vaporizing affects of the meltagun but are also quite inclined to attach a longer-ranged weapon to compensate for the relatively short range of the meltagun. As you already know, it is very useful when hunting tanks.
Like all Combi-Weapons in 8th edition, you can fire either/or as per normal, or shoot both at a -1 penalty. Because of its Melta attachment, you now have immense flexibility in the tankbusting and troopbusting compartment. Tanks and Terminators would stay the fuck out of your effective range and would make a good deterrent against charging TEQs.
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Sternguard Issue -
Ultramarines Sternguard -
Blood Angels Sternguard -
Deathwatch -
Storm Bolter Design -
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Tycho's -
Heresy Era -
Legion
Combi-Grenade Launcher[edit]
A Bolter with a Grenade launcher strapped to it, think of this as that particular Noobtube attachment you see on Call of Duty or Battlefield. Sometimes confusingly called the Auxiliary Grenade Launcher. As you can imagine, some have taken to calling this weapon a Noobtube as well despite the fact that on the tabletop it is not as overpowered as the ones you see in video games.
Due to its nature, it is useful for fighting large hordes of enemies or lobbing grenades over well entrenched positions, though why the Imperium thought it would be useful to attach a single-shot grenade launcher to an automatic rocket-propelled grenade launcher is anyone's guess (one might point out that this particular query has already been answered by the above reference to indirect/parabolic fir, but we all have off days).
Better question is why it isn't a belt-fed automatic grenade launcher with a box magazine. There is clearly room for it in the picture and a Space Marine can easily handle that. Fill the grenades with little melta-bombs for extra efficiency/effectiveness. (Bigga is betta, zoggin' 'umie!) Actually, since bolter shells explode after penetration, while good against armor, that effect is shit for clearing hordes. It's a bomb versus an RPG. The grenade part is to fuck up groups while the bolter cuts through lines of men and puts holes in armor. Besides, it seems that the weapon used by Forge Bosses in House Goliath seem to have fixed this issue.
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Primaris Marines variant
Combi-Plasma[edit]
The most prevalent type of combi-weapon among loyalists, combi-plasma guns are extremely useful. A popular tactic is to fire a plasma blast first, allowing the plasma to burn through whatever armor is present, then fire a bolt, which will be able to pierce the exposed flesh and explode inside the target. It is best used against MEQs, which in a Space Marine's combat tour, is a relatively common enemy to face.
Like all Combi-Weapons in 8th edition, you can fire either/or as per normal, or shoot both at a -1 penalty. Because of its Plasma attachment, you have an extremely versatile weapon that can deal with a wide range of infantry scaling from GEQs to TEQs. However, like all plasma weapons, you can overcharge to boost its strength and damage with the added risk of it blowing up.
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Sternguard Issue -
Devastator Sergeant -
Deathwatch -
Azrael's -
Legion
Combi-Grav[edit]
A bolter with a grav-gun attached to it. It serves the same purpose as a combi-plasma except it fires more shots and has an equal chance of hurting any vehicle, while plasma ranges from "ouch" against light vehicles to "all but useless" against the heaviest ones. However, due to the rarity of grav-guns, let alone a combi-grav, these weapons are seldom used unless it is for the most dire situations.
Like all Combi-Weapons in 8th edition, you can fire either/or as per normal, or shoot both at a -1 penalty. Because of its Grav attachment, it is excellent against vehicles and other 'heavy' units, although it is relatively poor against hordes of cheap infantry. Its status as a Grav weapon means that it is relatively rare in the 41st millennium.
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Devastator Sergeant -
Astartes Captain
Combi-Volkite[edit]
A pretty god damned rare combi-weapon even when compared to other rare combi-weapons like the Adrastus Bolt Caliver and the Disintegration Combi-Gun.
There used to be only one model of this weapon that appeared and it only made its debut on a special edition Praetor in Cataphractii Pattern Terminator Armour model kit during Warhammer Fest 2016. However, the Emperor's Children Praetor in Tartaros Pattern Terminator Armour was seen wielding a combi-volkite, so you no longer need to kitbash to get a model. Just buy it from Forgeworld.
As its name implies, the combi-volkite is essentially a Volkite Charger slapped on top of a normal Astartes Boltgun. The resulting combo actually complements both of the weapons' strengths and negates their weaknesses. The Bolter for example, offers range, accuracy and armour-piercing capabilities whilst the Volkite covers it by targeting vast swathes of MEQS and other infantry at close range.
Horus Heresy 2.0 rule changes allow models with Combi-Weapons to fire both weapons at once with no penalties even if they don't have the Firing Protocols (X) rule, in contrast to Warhammer 40k post-8th edition requiring a -1 aim roll for doing the same. Combi-volkites are classified as minor combi-weapons like the combi-flamer and combi-grenade launcher. Minor combi-weapons can fire their secondary weapons the whole game without running out. Combi-plasmas, combi-meltas and combi-disintegrators are magna combi-weapons that have the One Shot rule on their secondaries.
Infernus Heavy Bolter[edit]
Added in with the Deathwatch army, it's just as it sounds, a heavy bolter with an under-slung heavy flamer, whoever made this must have been high off their tits because that shit is ridiculous. Maybe they've been hanging around orks too long because this sounds like a serious case of wanting more Dakka. You know though, it sort of makes sense that the guys dealing with Xenos filth all the time would take the most inspiration from them.
Besides, when you only have a squad and are supposed to fight things an entire company of Astartes would normally face, you need as much dakka as possible. In any case, combining a heavy bolter with the ability to wipe out anyone who manages to get through the hail of fire without stopping the bolt-throwing is pretty dang good.
On tabletop, it costs 14 points and can be fired together like other combi-weapons, imposing a -1 to-hit penalty which the auto-hitting Heavy Flamer component gives precisely 0 shits about. Bear in mind that if you're shooting on the move, the Heavy Bolter already has a -1 to-hit penalty. The frag cannon is 6 points more, but simply does the job far better.
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Side View -
Front View
Adrastus Bolt Caliver[edit]
Adrastus Bolt Calivers AKA The Golden Gun is a type of Combi-Bolt Weapon used by the Adeptus Custodes.
As you can imagine, these guns are one of the best anti-infantry weapons of the Imperium. Due to the size of the Golden Bananas, these hybrid guns are used as heavy weapons by the Custodes and utilize 'Adrasite' disintegration beam technology banned from the wider Imperium. This essentially makes them as Imperial Gauss Blasters but fluff-wise better and quicker to work but shorter ranged. This combination weapon is able to unleash a fusillade of explosive rounds at long range with the potency of a Heavy Bolter or fire a short range disintegration beam able to rip a target apart at the molecular level. Their golden color and its properties makes them officially Awesome.
Only the Sagittarum Guard are given the privilege to be issued and trained with these golden weapons of war.
In the Horus Heresy tabletop, it is a 30" Assault 3 Heavy Bolter with a Disintegration Beam welded onto it. Distinctly stated as being two functional weapons with unlimited uses, but only one can be used a turn.
On 40k tabletop, however, it is much better as it has 2 profiles: the first one is Bolt Volley which is a 36" Assault 3 Heavy Bolter (S5 AP-1 D1) or a Disintegration Beam which is a 15" Assault 1 S5 AP-3 D3. As usual with combi-weapons, you can fire both profiles during a single shooting phase at the cost of getting -1 on your hit rolls, which is mathematically worth it in the case of the caliver.
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First Side View -
Second Side View -
Front View -
Left View
Disintegration Combi-Gun[edit]
A rare weapon from the Dark Age of Technology, the disintegration gun is actually only available in the forms of a pistol or combi-weapon. It does exactly as the name suggests, it disintegrate things. In 7E, the disintegration gun itself has a very similar statline and effects to the Adrathic weaponry of the Custodes, also described as being disintegration weapons, so one can assume the Adrathus Bolt Caliver (an Adrathic Destructor mounted on a Heavy Bolter) is pretty much a beefed-up version of it. With weapons like this, one must wonder how fucked up the Age of Strife was that shit like this wasn't enough to save humanity from being mulched.
Despite being powerful and looking pretty damn sweet, this weapon was only available on the limited edition 30th anniversary "Imperial Space Marine" model, so you had to deal with eBay scalpers or learn how to convert one of your own if you want one. With Horus Heresy 2.0 turning the combi-disintegrator into a regular combi-weapon that can be taken on certain units (Nullificators and HQs, mostly), one would think that GW would include the bits necessary to see this weapon in a more modern context... but then again, GW doesn't think like normal people, and thus we're still waiting for combi-weapon kits for these and the grenade launchers.
Inquisition / Assassinorum[edit]
Combi-Needler[edit]
A weapon used by the Ordo Malleus. A Bolter with a Needler integrated within it, intended to be used against creatures like daemons that are extremely difficult to injure. This Combi-weapon is used only by the Inquisitors and Acolytes of the Ordo Malleus as the materials and expertise needed to craft these weapons is difficult and hard to acquire. A variant of this Combi-weapon also serves as the primary weapon of Eversor Assassins.
The Combi-Needler is used by non-assassins and it is a relatively easy to manufacture weapon in contrast to the Executioner Pistol. Of course, as a Needler, it is a pain in the ass to shoot the damn thing, making it the most overcomplicated trainwreck ever made. Seriously try shooting the Needler right after dealing with the recoil of the Bolter whilst factoring in the dual laser-needle combo conundrum.
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Pistol Variant -
House Escher
Condemner Boltgun[edit]
Also called the Combi-Stake Crossbow. Used by Ordo Hereticus and Sisters of Battle, this is a bolter combined with one-use crossbow. The cool point is that the crossbow bolt is filled with a mix of holy promethium and some anti-psychic shit produced by the Golden Throne.
So a direct hit from the crossbow component of the Condemnor Bolter will therefore not only deal a severe physical wound to an enemy psyker, it will also send his or her power spiraling out of control, consuming the user in a storm of untrammeled psychic energy. So it's not only going to burn the witch's body, but also burn down his very soul (which is crunch wise auto-peril to any psyker target).
On tabletop, it counts as a master-crafted weapon with 24″ range. Its stats is Rapid Fire 1, S4, Ap-1, 1 Damage, 3 Damage plus the additional auto-peril vs. Psykers as aforementioned.
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Front View -
Top View
Executioner Pistol[edit]
Used by Eversor assassins, this is (in DH) a combi-needle pistol, or (in WH40k) a pistol that fires poisonous needle shaped bolt rounds. As a result, the Assassin can fire both explosive Bolts or needles composed of a crystallised neurotoxin, sedative or interrogation narcotic into his victim, as the situation demands. The weapon's Needle Pistol toxins are so potent that whenever a target is hit by a shot it kills the victim almost outright.
It is this versatility, combined with the exquisite craftsmanship of every Executor Pistol, that makes it such a popular choice for one of the Imperium’s sanctioned assassins. The weapon incorporates the heights of arcane tech-lore in its construction. It possesses a bi-stabilized targeting sight, and its polymorphic grip is genetically coded to the individual Assassin. Thus, even if an opponent were somehow to gain control of an Executor Pistol, he would be unable to fire it. Changing the weapon’s programming to recognize a different user requires access to secret Officio Assassinorum facilities, something that is almost impossible even for most members of the Inquisition.
The weapon is counted as a 12" Pistol 4 with S4 AP-1 D1 and re-rolls failed wounds against INFANTRY.
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Left View -
Right View
Needlespine Blaster[edit]
Used by the Adamus assassins. The Needlespine Blaster is the slightly larger brother of the Executioner Pistol, sporting a Needler at the top and a Bolt Pistol at the bottom. In terms of function, it is quite similar to that of the Executioner Pistol as both of them are essentially a form of combi-needlers. The biggest difference is that the Needlespine Blaster's scope is unusually on the side of the gun, rather at the top.
Given the close-range nature of the Adamus, the weapon would inadvertently be constantly compared to the Executioner Pistol because of how much these two share the same niche. It can be argued that the Needlespine, being the bigger, heavier gun, would offer more range than the Executioner at the expanse of it being harder to handle. But it is only speculation for now.
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Alternate View
Squats[edit]
Autoch-Pattern Combi-Bolter[edit]
The Leagues of Votann have their own equivalent of a Storm Bolter and Combi-Bolter.
The Autoch-Pattern Combi-Bolter is a double-barrelled design weapon that follows a similar function to both the aforementioned weapons; being two Autoch Pattern Bolters strapped into one single firing mechanism. Due to the increased complexity and maintenance of such a weapon, only high-ranking Kin such as the Kâhls or the Hearthguards are granted the privilege to weild these things.
The Combi-Bolter comes in two variants, the normal looking one that looks like a Storm Bolter/Combi-Bolter and the giga-chad version mounted on a RAM Shield and used by the Hearthguards.
Tabletop wise, it counts as a 24" HunTR 4 Bolter. Lots of Dakka indeed.
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Kâhl Twin-Linked Variant -
Hearthguard RAM Shield Variant -
Chaos Space Marines[edit]
Combi-Bolter[edit]
Also known as a Twin-linked Bolter, the combi-bolter was basically a pair of boltguns duct taped together to create a more dangerous weapon.
It was used by the Space Marine Legions during the Great Crusade. However, it has been replaced by the Storm Bolter among the Imperium, but it still sees some use here and there due to most Astartes and the Mechanicus keeping some around as relics. But it is still mainly used by Chaos Space Marines, more specifically by the Chaos Space Marine Bike Squadrons where they can perform dakka in a quick and easy fashion.
Due to the fact that a Storm Bolter has twin recievers and hammers which allows for a smoother and faster fire rate, in theory, the Combi-Bolter should be inferior in almost every aspect, as you are basically firing two barrels with a split hammer. Think of it as this way, the Combi-Bolter functions similarly to a double-barrelled, magazine fed, fully automatic shotgun (granted that does sound pretty fucking awesome).
Despite the differences, it is functionally identical to a Storm Bolter in 8th Edition.
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Dark Angels Combi-Bolter
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Ditto
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Phobos Pattern Combi-Bolter
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Tigris Pattern Combi-Bolter
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Inferno Combi-Bolter
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Ditto
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Umbra-Ferrox Pattern Combi-Bolter used by a Seeker
Orks[edit]
Kombi-Rokkit Launcha[edit]
The Shoota/Rokkit Launcha gives the user a single side-mounted Rokkit Launcha with a single Rokkit to use against enemy tanks and armored vehicles. Great for when your Shoota Boyz needs a little bit more anti-vehicular punch and weight or if you need more Tankbustas but don't want to waste any more points. Considering orkish ballistic skill it's probably going to miss when you fire it or explode in your face if the wiring is all wrong.
Because of its Rokkit attachment, it would give the Orks some needed anti-armor in an army that is vulnerable from mass artillery and machine gun fire. A Kombi-Rokkit allows your Orks to have a chance (albeit a low one given Ork accuracy) to pop some armour before it gets too hot.
In 8th Edition, the new rules for Kombi-weapons allow these weapons to see a lot more use, as anyone who takes these doesn't have to be so tight-arsed about firing their anti-tank weaponry anymore. Unfortunate with Orky BS it is hard to justify the expense.
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Meganob -
Common Variant
Kombi-Skorcha[edit]
An orkish version of the Combi-Flamer with the more powerful Skorcha (Heavy Flamer) attached to it instead of a Flamer. The Ork version of a combi-weapon is a Shoota with something attached to it instead of a Boltgun with something attached to it. Great for crowd clearing as well as boosting the CQC killyness of your Orky Boyz, and unlike the Kombi-Rokkit Launcha, you don't really need to worry about accuracy.
The Kombi-Skorcha in 8th edition became ridiculous especially when you have all your Nobs or a Big Mek equipped with one. This thing is capable of unleashing 2D6 Heavy Flamer shots with 6 str5 and 4 str4 shots. Have a bunch of Nobs equipped with one and have them ride on any troop carrying vehicle and let it rip.
In 9th edition, the new Kombi-weapon rules works much better for this weapon in contrast to the Kombi-Rokkit, especially since the auto-hitting Skorcha isn't affected by the -1 To Hit for firing both weapon profiles. Notably, you can Advance and still spray flames and bullets. The Skorcha's profile are as follows: Range 8" Assault d6 S5 AP-1 D1.
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Meganob -
Common Variant
Twin-Linked Shoota[edit]
Think of this as the Ork's equivalent to the Chaos Space Marines Combi-Bolter. The Twin-Linked Shoota is basically two large Shootas or Big Shootas duct-taped together from side to side. The Twin-Linked Shoota is often used commonly by Ork Warbosses as it gives them sufficient dakka before closing in for the kill and krumpin' his enemies, but larger variants're also installed on light vehicles such as Warbuggies and Deffkoptas. It provides greater accuracy than your standard everyday Shoota.
The Twin-Linked Shoota is essentially like the Combi-Bolter, but with more Dakka and even less accuracy and range. Seriously, it is a pretty impressive feat even by Ork standards to create a weapon that out-storm the Stormbolter and Combi-Bolter respectively.
Tabletop wise, it is basically a Big Shoota with double the shots and double the price.
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Front View -
Back View
Gallery[edit]
Twin-Linked Shoota[edit]
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Common Variant -
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Kopta Rokkits[edit]
Although they are called Kopta Rokkits. They could actually be found on other Ork vehicles.
A particular innovation of the Orks, the twin-linked Rokkit Launcha somewhat mitigates the Ork's general inaccuracy to make Warbuggies and Deffkoptas more threatening, giving these small but fast units a good chance of hitting the mark. The much heavier Gorkanauts and Morkanauts also carry the equivalent of this, though in their case it's actually just two separate Rokkit Launchas mounted next to each other.
In terms of crunch, they BS 5+. No way. Koptas with these aren't as reliable as other Ork anti-vehicle weapons/units. But way too expensive to be actually fielded that way.
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Deffkopta Mount -
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Morkanaut Mount -
Gorkanaut Mount
Real Life[edit]
Yes, these actually exist. Yes, it is Awesome.
The earliest combination weapons sought to combine the ranged firepower of pistols with the close combat of a melee weapon, usually pistol-swords or pistol-axes. Because the components on a pistol didn’t hold up well to physical abuse and the added weight made the melee weapon part awkward to wield on top of making the pistol part difficult to aim, these were not widespread. The only version that became successful was the bayonet mounted on a rifle. Others combined the mechanical reliability of a crossbow with an undermount wheel-lock pistol.
Compared to twin-linked weapons in 40k, in real life this was never done with military small arms. The vast majority of twin-linked weapons are gun turrets specifically intended to destroy aircraft. Against a ground target, a single barrel weapon is sufficient. But against a fast-moving aircraft, the best way to increase your hit probability is to spam as many bullets as possible. We do have one example of a twin-linked M1911 pistol that was made for the lolz, and an Italian SMG from WWI that started as turret gun for biplanes before being handed to ground troops out of sheer desperation, but users quickly realized that any potential benefit to doubling firepower is lost on the added weight, awkward handling, and the fact that neither bullet will hit exactly where you aim.
But, we added the qualifier up there of 'military' small arms for a reason, and double barreled weapons are fairly common as hunting weapons such as the double barreled shotgun. In these cases the ability to take a second shot quickly on game that might be running away, or running toward you if your going after big game like bear, elephant or even boar, is more important then weight, and if you do have a bear running down on you the ability to take a second shot before you get torn apart is of the upmost importance.
Below are some specific examples of combinations weapons.
LeMat Revolver[edit]
Are you depressed about your nine-shot revolver not having more firepower? Well worry not, as the axle used by this gun's cylinder also doubles as a smoothbore barrel, allowing you to fire a shotgun blast with just a flick of the small lever atop the hammer! Amazing!
Grenade Launcher[edit]
The only major combi-weapon the military uses. Examples include the M203, which clips under the barrel like a bayonet. It can also be reloaded, unlike pre-8th Edition 40k variants, and has mostly replaced the non-automatic Grenade Launcher (which still has its uses, as a longer barrel means you can launch grenades much farther away).
Shotgun[edit]
Not as common as an underbarrel grenade launcher, the military also has a few different shotgun attachements, such as the KAC Masterkey or M26 MASS. Used for door breaching more than anything else, troops can also load up specialized rounds for everything from bean-bags to taser shells to even small grenades.
Combination Gun[edit]
The major combi-weapon outside the military, meanwhile, is the combination gun. Essentially, this is a way to give a hunter the ability to almost instantly line up and fire another shot if he misses by simply adding a second barrel to the gun, while additionally it is often used to create a gun that can fire multiple forms of ammunition by making one barrel rifled and the other smoothbore. In Yurop these are called "drillings" (or vierlings for four barrels and so on) or "cape guns" and if you're a disgustingly rich Nob looking to spend a lot of money on the gun equivalent of a BMW then these cater specifically to you. Sometimes three barrels are used so the gun can simultaneously be loaded with a rifle round, a shotgun slug, and bird or buckshot.
Either way, these later two cases give it a niche military use as a survival weapon for aircrew, which can range to the logical style of a light and simple rifle with a shotgun barrel, to a high-end and expensive 'survival' weapon that's a 1-to-1 copy of a civilian big game rifle and weighs so much you can't parachute out with it (so have to hope you can recover it from the wreck once you land). Yes, the last one actually happened, Herman Göring used them as standard issue for the Luftwaffe, because of course the obese, ostentatious manchild decided it was a good idea. Less flashy and more economical versions of the same concept include the USAF's M6 survival rifle, or the Soviet Union's TP-82 Cosmonaut survival pistol.
Another example was the Swedish NIVA XM1970 in the 1970’s. Not content to merely have Carl Gustav recoilless rifles and regular guns distributed within a platoon and wanting something with more firepower than rifle grenades, the Carl Gustav tried to mate a bullpup rifle with a recoilless rifle to give a soldier more dakka. Unfortunately they never figured out how to trim weight and size down. And nobody in the military was even interested in buying the thing.
But nobody out-riches the US Army, who tried to make their own combi-gun called the OICWYDT, combining a crummier version of an M4 carbine bolted to a computerized laser-ranged airbursting grenade launcher. The smart grenades for this thing cost more EACH than the gun it was combo-ed with. The whole thing weighed about 30 pounds and was as easy to carry as a similarly heavy sack of dog food. Eventually the combi-gun idea part of the whole deal was scrapped and the smart grenades were tested alone as the XM25 before being dropped for being too expensive and not reliable enough. The South Koreans built a similar weapon, the K11, which was likewise cancelled. The Chinese, meanwhile, came up with the QTS-11, which tries to solve these issues by making the grenade launcher portion a single-shot bolt-action weapon with less electronics in the warheard. It remains to be seen if this approach is at all more practical, because its still expensive hardware of questionable efficacy.