Bolter sizes/layout

[Meest]

Noticed in 40k art works that bolt pistols or human sized bolters look to be setup in the same way as modern firearms. Compared to upscaled bolters especially boltguns the bore axis seems really low compared to where the extractor/ejector opening is. Also what are the multiple barrel looking things protruding above or below the muzzle? Why is it more prevalent the bigger bolters get?

[Todeswind]

Because it looks cooler on the box art more likely than not, the Games Workshop design team puts far more thought into esthetics than function. There is probably a fluff explanation for it but frankly I'd be surprised if it were based on any reason that weren't retroactive technobabble. Unless you're talking about a combo-bolter in which case, yes those are other barrels.

It's also probably worth noting that the bolter doesn't fire bullets. It shoots rockets.

[Ahriman238]

Combi-bolters? Basically like an assault rifle with a grenade launcher mount, except instead of grenades its a flamer/melta/plasma/backup bolter.

[Cykeisme]

Occasionally artistic depictions of what are supposed to be the precise same model ("pattern") of weapon, like an Astartes Godwyn-pattern boltgun, are drawn with slightly different proportions and size, though it's usually recognizable as being what it's supposed to be.

EVEN in universe, I guess you can think of all the artwork as just that.. stylized artwork.

[Black Admiral]

Combi-bolters? Basically like an assault rifle with a grenade launcher mount, except instead of grenades its a flamer/melta/plasma/backup bolter.

Partly correct. "Combi-bolter" refers to a specific type of combi-weapon, one which is essentially two bolters stuck together (and was a predecessor to the stormbolter). A combi-weapon is usually referred to with the name of the additional weapon, e.g. combi-plasma for one with an under-barrel plasma gun, combi-melta for one with a meltagun so affixed, and so on.

[Meest]

The part that I can't figure out is the little protrusion on top of the barrel. And why in general the upper receiver is huge wtf is going on up there. Do bolters literally have machine spirits? Electronics or whatever is needed to support an AI and maybe link up to the armour with some wireless tech?

[andrewgpaul]

The bit above the barrel is probably some sort of gunsight. Depending on the author, the gun can interface with the helmet autosenses to give a HUD targeting display and other status indicators. On top of that, there's the "sinister/dexter ejection mechanism" (the gun can switch the side it ejects the casings from on the fly, depending on which hand the Marine's holding it in), and signal connections from the handgrip to the palm of the armour. There's also a status display on the other side of the gun, where the safety/shot selector switch is on the picture you link to.

Primarily though, it's because Jes Goodwin was an art student, not a soldier, before being one of GW's sculptors.

[Elheru Aran]

It's notable that earlier models of bolter were much more straight-lined from the receiver to the barrel; it was basically a tube in a box with a grip and a magazine sticking out of it, not too unlike the Sterling SMG, actually.

The tube on top of the barrel is indeed an auto-aimer or a sensor with gunsight function. You note similar protrusions on the boltpistol, stormbolter, and heavy bolter, so it's obvious there are onboard electronics of some form; there's also an ammunition counter as well, I believe.

Note, for example, the 'Phobos' pattern, which is a modernized version of the original Space Marine bolter:



Then that turns into the Umbra pattern:



The Phobos is similar to the 'newer' Godwyn pattern in layout with the ejection port above the line of receiver and barrel; presumably the Umbra was adopted for ease of manufacture with its simpler lines and perhaps simpler mechanisms.

Here's an 'improved' Umbra pattern:



These have an electronic gunsight as well as a larger capacity magazine added.

On occasion one sees bolters being packed by Inquisitors or Imperial stormtroopers, and due to the screwed-up scales that GW models are at, they're the same size as the Astartes bolter models. This can be explained by the fact that they're simply the same style, if not size, in emulation of the Emperor's Angels... otherwise I think people might notice the 8-foot-tall Guardsmen

[Lord Relvenous]

The top protrusion is a laser designator/rangefinder/gunsight/thingy, depending on where you read the description, as stated before.

The bottom protrusion is a bayonet lug.

[andrewgpaul]

It's notable that earlier models of bolter were much more straight-lined from the receiver to the barrel; it was basically a tube in a box with a grip and a magazine sticking out of it, not too unlike the Sterling SMG, actually.

The tube on top of the barrel is indeed an auto-aimer or a sensor with gunsight function. You note similar protrusions on the boltpistol, stormbolter, and heavy bolter, so it's obvious there are onboard electronics of some form; there's also an ammunition counter as well, I believe.

Note, for example, the 'Phobos' pattern, which is a modernized version of the original Space Marine bolter:

Then that turns into the Umbra pattern:

Is that the official order? Out of universe, the design on which the Umbra is based came before the design on which the Phobos is based. Mind you, the longer barrel on the Phobos is reminiscent of the weapons carried by some of the miniatures of early marks of power armour:


(specifically the Ultramarins in Mk1 armour on the left)

On occasion one sees bolters being packed by Inquisitors or Imperial stormtroopers,

Not to mention underhive gangers; the Delaque and Cawdor Leader miniatures are carrying - in the case of the Delaque leader, firing one-handed - bolters identical to the Marine miniatures of the time.

[Connor MacLeod]

Bolters invariably remind me of the SMG types that don't stick the magazine in the grip (like an Uzi or MAc-10) the relatively short barrels, the lack of a stock, etc. Given that Astartes are supposed to be close-range troops (boarding ships, drop pod assualts, etc.) it probably makes sense. The only reason they tend to get rifle ranges from them (EG like a bolt pistol in Angels of Darkness) is probably because of the power armor offering stabilization assistance (I believe Uriel demonstrates this in Warriors of Ultramar.)

[Thinktank]

Bolters according to the fluff fire a 25mm conventional charge initiated gyrojet slug.
They do not need a long barrel or stock when carried by Space Marines due to all their
mass and enhancements and whatnot.

From Here: http://warhammer40k.wikia.com/wiki/Bolter

Description:
Appearance:
The Bolter is a large, .998 calibre assault rifle. It has a much greater mass than most standard-issue rifles such as the Lasgun, although it is slightly shorter in length. Unlike most rifles, it lacks a stock, resulting in a grip much like a pistol's or a submachine gun's. A Space Marine's bulky Power Armour would make shouldering a stock an awkward experience, but Power Armour is most likely also able to compensate for vibrations and oscillation, making a stock redundant. Stocks are sometimes used, however, with an extended barrel and an M40 Targeter System to transform the Bolter into a sniping weapon system. These sniper Bolters, known as Stalker Pattern Bolters, are most often used with Stalker Silenced Shells.

Standard Bolter Round:
Bolter ammunition (a bolt) is primarily a solid slug. Conventional solid slugs utilise a propellant charge contained in a casing that, when ignited, forces the bullet out of the barrel. In contrast, a bolt is self-propelled; it features its own integrated solid propellant that propels the bolt at high speeds, essentially acting like a miniature rocket. The propellant itself is shaped to control the bolt's direction and speed; however, this method of rocket propulsion would normally warp the barrel due to gas pressure. The Bolter uses an ingenious method to prevent this.

As well as the rocket propellant, a tiny amount of conventional charge is also utilized. This charge is just strong enough to force the bolt out of the barrel and ignite the bolt's propellant. The rocket-propellant is carefully fused to ignite just after leaving the barrel, alleviating any possibility of pressure build-up. The bolt then accelerates away towards the target under its own power.

The standard Bolter ammunition is designed to penetrate the target and then detonate, causing immense damage to the target and leaving little opportunity for survival.

[andrewgpaul]

The actual calibre isn't really defined. Some sources give one - which may or may not remain constant, from one source to another - but that 40K wikia page is typically badly-sourced. All the images are unlabelled fan-art, for a start.

[Connor MacLeod]

They're .75 calibre. Heavy bolters are 1.0 calibre at least in some sources, though this can range to "fist sized" in others.

Of cource it also ignores the fact some bolters fire cased ammo (and even the ammo is shown as cased) as well as "caseless" (Eg rocket propelled)

[andrewgpaul]

That what I mean about some sources contradicting others. At least one source says that heavy bolters, bolt guns and bolt pistols use the same ammunition, with the only difference being magazine capacity and rate of fire. That might have been a rules abstraction, but I'm not convinced about that.

As for the rounds being .75 calibre, what is the source for that? Not that I'm doubting you, but it seems reasonably accepted and yet I can't remember where it comes from.

[Ritterin Sophia]

They're .75 calibre. Heavy bolters are 1.0 calibre at least in some sources, though this can range to "fist sized" in others.

IIRC, According to Death Watch all Astartes bolt weapons fire 1.0 calibre.

[andrewgpaul]

According to page 146, "the standard bolter round is .75 calibre ...". All it says of heavy bolters is that they "fire rounds of a much larger calibre...".

[Connor MacLeod]

yeah checking Deathwatch I only find the usual .75 calibre fluff. It's also been mentioned as far back (as I know) in 3rd-4th edition (I know the Spac Marine codexes did, and I think the 3rd edition core rules did - they tended to have alot of technical data surprisingly.)

Storm of iron also mentions normal man sized bolters as firing .75 calibre rounds so...

And yeah I've seen the whole "All bolters use the same ammo" while I've seen other sources say bolters fire bigger rounds like andrew noted. I don't remember WHERE I saw the 1 inch calibre, though. It wouldnt surprise me if there was some variation in bolt design or calibre, despite what the fluff says, because the fluff is always adamant about how bolters work, but sources even disagree about that (its rocket propelled, its a gyrojet, its not a gyrojet, it ejects casings, its caseless.. it explodes, it doesn't explode..) so I've just thrown bolters into the same pool as every other weapon of 40K - the inconsistencies mean different classes and variations. I imagine .75 calibre gets mentioned so much because most are familiar with it.

Another interesting thing is that many sources (like Deathwatch) list them as having a "solid metallic core" along with "depleted deuterium" - which would mean metallic hydorgen, which to my understanding would be a pretty nasty explosive. Then again there's the depleted uranium from storm of iron and various other sourcs (some suggesting IIRC they might actually be small scale fusion explosives )

And then of course there's that storm bolter penetration issue (8 inches of plasteel., IIRC) and the whole Eisenhorn malleus bolt pistol recoil (knock a 400 kg augmetic witch on her ass...)

[Eternal_Freedom]

If you want a source for the 25mm calibre, look no further than Space Marine (the recent game). When you first acquire the Bolter, it gives you a little background, stating that the standard-issue SM Godwyn-pattern bolter fires .998 calibre rounds.

[Connor MacLeod]

Oh goody more consistency problems. So now it fires a round as big sa some stubbers, autocannon and heavy bolters

[Elheru Aran]

(snip)

Is that the official order? Out of universe, the design on which the Umbra is based came before the design on which the Phobos is based. Mind you, the longer barrel on the Phobos is reminiscent of the weapons carried by some of the miniatures of early marks of power armour:

I have no idea if it's the 'official' order in which bolters evolved, but that's how Forgeworld presents it. They don't have a transitional weapon between the Umbra and the Godwyn yet, though, which is slightly curious because proportionally at least the Umbra and Phobos seem rather longer than the Godwyn. I could be seeing things, of course...

It does somewhat make sense though. With the thunder armour manufactured on Earth, they can supply a more complex weapon to smaller numbers of troops, hence the Phobos pattern; but with the hundreds of thousands (if not millions) of Space Marines during the Crusade, a simpler and easier to manufacture weapon is called for. This becomes especially acute during the Heresy, when much of the Imperium's manufacturing was shut off from the Legions. After the Heresy and when the war winds down, then they have the breathing room and fewer Space Marines to supply weapons to, hence reverting to a more complex weapon with more advanced equipment, the Godwyn.

That does make me wonder why Chaos Space Marines pack Godwyn-type bolters, though... logically they should have Phobos or Umbra patterns for the most part. Of course, in universe either they simply copied the design (hardly unprecedented) or stole a few convoys' worth of Imperial supplies.

Re the size: remember that it's using a pistol-length cartridge, rather than a rifle-length cartridge. Granted, at 25mm it's one heck of a big pistol round, but it's still a fairly compact round versus what would be something like 8 or 9" long at a rifle length proportional to the caliber size. Think something not unlike the 40mm grenade round versus a 30mm GAU-8A Avenger shell. This probably also allows them to pack a pretty good number of rounds into their magazines, as well...

[Brother-Captain Gaius]

If you want a source for the 25mm calibre, look no further than Space Marine (the recent game). When you first acquire the Bolter, it gives you a little background, stating that the standard-issue SM Godwyn-pattern bolter fires .998 calibre rounds.

Are you sure? "998" has always been given as the most recent model of Godwyn, never its caliber.

Though it's not like Space Marine is all that fluffy anyway.

[Eternal_Freedom]

That's what I recall from my most recent play-through of the game. I may be wrong, but I'm fairly confident of that number.

[Thinktank]

They're .75 calibre. Heavy bolters are 1.0 calibre at least in some sources, though this can range to "fist sized" in others.

Of cource it also ignores the fact some bolters fire cased ammo (and even the ammo is shown as cased) as well as "caseless" (Eg rocket propelled)

The .75 and 1.0 calibers comment you made, makes sense to me.

In 1st edition bolt pistols looked to be much smaller than a "rifle" scale bolter. They looked to be around .50 cal in comparison to their larger kin. But alas that most certainly changed over the years and editions.

The article I linked kind of explains the part I bolded in the quote.

It uses both types of propulsion. The bolter shell uses the small cased charge to start the gyrojet projectile on it's way, then the rocket charge kicks in. It is a conventionally initiated self propelled round. How this is accurate must require all the "hard to mass produce" technology that makes bolters "so special".

[Kojiro]

Back in the day bolt rounds were universal- bolt pistols, bolters and heavy bolters all fired the same round. No idea why heavy bolters were more powerful). But in principle all bolt weapons work similarly, if not for the scale/RoF.

What confuses me, particularly with the heavy bolter, is what the hell all that extra material is used for? When you get right down to it a gun can be a pretty compact thing. Bolters and heavy bolters seem to have massive amounts of 'body' to them which just doesn't seem to serve any purpose.