Combi-weapons are specialized weapons in Warhammer 40,000, mainly used by the Imperium of Man, 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 that's something new compared to previous editions, shoot both at the same time at the cost of a shooting penalty. They come in several varieties.
Generally speaking, Combi-weapons 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.
A boltgun with a flamer attached to its underside. When you want both the firepower and armor-cracking effects of the Bolter but also want to have the horde cleansing affects of the trusted Flamer, accept no substitutes. Especially useful for close combat situations. 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.
A bolter with a meltagun attached to its underside. 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 is also quite inclined to attach a more 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.
A Bolter with a Grenade launcher strapped to the side, 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 has taken calling this weapon a Noobtube as well despite the fact that on tabletop it is not as overpowered as the ones you see in other 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 fire 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 vs an RPG. The grenade part is to fuck up groups while the bolter cuts through lines of men and puts holes in armor.
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 AP with the added risk of it blowing up.
A bolter with a gravgun attached to its underside. 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 Gravguns, let alone a Combi-grav, these weapons are seldom used unless it is of 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 attatchment, 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.
Infernus Heavy BolterEdit
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, I think you're probably right on that one, 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.
Adrastus Bolt CaliverEdit
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.
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, 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 is only available on the limited edition "Imperial Space Marine" model, so you're gonna have to deal with eBay scalpers or learn how to convert one of your own if you want one.
Inquisition / AssassinorumEdit
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.
Also called the Combi-Stake Crossbow. Used by Ordo Hereticus and Sisters of Battle, this is a bolter combined with one-use crossbow. Yeah, it sounds pretty pathetic. 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).
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.
Chaos Space MarinesEdit
Also known as a Twin-linked Bolter, the combi-bolter was basically a pair of boltguns welded 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 is still used by Chaos Space Marines, more specifically on the Chaos Space Marine Bike Squadrons where they can perform dakka in a quick and easy fashion. In 8th Edition, it is functionally identical to a Storm Bolter.
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 anymore 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 armor before it gets too hot.
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.
Think of this as the Ork's equivalent to the Chaos Space Marines Combi-Bolter. The Twin-Linked Shoota is basically two large 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. 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.
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, these were not widespread. The only version that became successful was the bayonet mounted on a rifle.
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 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 shot gun. 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.
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!
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 basically replaced the non-automatic Grenade Launcher.
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.