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I'm curious why the Heavy Bolter is such a boxy weapon. I actually don't mind the standard Boltgun, since it doesn't fire particularly fast. But the HB is different. It is a fully automatic grenade machine gun. And yet there is no heat dispersal that I can see.


M2 Browning Machine Gun. Equivalent to a 40K Heavy Stubber. These things produce a lot of heat because of the friction caused by bullets passing through the barrel. If you fire a machine gun continuously, you're going to melt the barrel. That's why you see those big jacket holes (thanks for the correction Amanita) around the barrel, they are there to disperse the heat between bursts.

With a fully automatic weapon like the Heavy Bolter firing massive shells at a high rate of fire, having a heat sink or a means to prevent the barrel from melting seems like a no brainer. But at least on the current models, there seems to be none. Is it because Games Workshop doesn't properly think these things through? Or because a featureless rectangle is easier to mold than a gun?

Or am I just sperging out?

Bolters are more akin to small rockets then bullets. They have a small boosting charge to push them out of the barrel, then are self propelled to their targets. They don't need the large initial push that modern guns do. Nor do they require the rifling of the barrel, and ensuing friction, for stability in flight. You'll notice that they have little stubby barrels, not the long one of the ma deuce.

And this is before you start getting into future composites and metals.

While they may overheat from time to time, I think it's only going to be when cinematically appropriate in whatever story is being written.

"The Heavy Bolter sings praises to the Emperor in a voice that never tires"

Given the massive chunk of weapon that resides behind the receiver in most HB models, it would be relatively easy to fit a magic cooling system

Basically, GW weapon design tends to leave a lot to be desired from the technical point of view...

Autoguns and stubbers are roughly equivalent to modern weapons, so they show (some) modern aesthetics.

Bolters are the product of technology and materials so advanced that they might as well be magic. They care little for such trivialities as "heat dispersion" and "rifled barrels".

Well its shear mass ought to conduct away heat relatively well. And you're right about all that extra space. Maybe the tube that comes out the back is actually a cooling pipe that circulates liquid.

Applying real world physics to a fictional weapon in a fictional universe isn't going to work. GW could easily just say that bolters of all kinds are made from a special alloy that won't melt at the heat produced by continuous fire.

All that being said, part of the beauty of 40k and this hobby in general is that if you don't like it, you can convert it!

I can't see the need for heat dispersion, as bolts are just little rockets that only use the barrel as a launch tube. It's not like there is a continuous string of explosions being contained behind them like modern bullets.

I would imagine in real life that the majority of a bolt's thrust happens after the leaving of the barrel, with only a small beginning thrust building to "cruising speed". Unlike a bullet, which needs all of it's force at the beginning. Then the heat would be minimal.

 AegisGrimm wrote:
I can't see the need for heat dispersion, as bolts are just little rockets that only use the barrel as a launch tube. It's not like there is a continuous string of explosions being contained behind them like modern bullets.

I would imagine in real life that the majority of a bolt's thrust happens after the leaving of the barrel, with only a small beginning thrust building to "cruising speed". Unlike a bullet, which needs all of it's force at the beginning. Then the heat would be minimal.

True that. Now I think of it I'm guessing most of the heat made by a traditional gun is friction of the bullet traveling down the barrel. After all it is always the barrel that gets hot and not the firing mechanism. If it's a rocket it doesn't need rifling so it doesn't need a tight barrel. All it really needs is something to hold it in position and point it in about the right direction.

I just came to a depressing realization...bolters are basically oversized bottle rocket launchers (the firework, not the science project).

 Nevelon wrote:
Bolters are more akin to small rockets then bullets. They have a small boosting charge to push them out of the barrel, then are self propelled to their targets. They don't need the large initial push that modern guns do. Nor do they require the rifling of the barrel, and ensuing friction, for stability in flight. You'll notice that they have little stubby barrels, not the long one of the ma deuce.

And this is before you start getting into future composites and metals.

While they may overheat from time to time, I think it's only going to be when cinematically appropriate in whatever story is being written.

"The Heavy Bolter sings praises to the Emperor in a voice that never tires"

The initial charge is still roughly equal to a normal bullet, hence why bolters are still lethal at point blank range.

A bolt round is a normal bullet that has had a rocket added along with an explosive charge. They benefit from both rifling and gyro-stabilization for accuracy.


When you consider the size of the gun, the barrel is not much shorter than any of our modern weapons. Its just largely contained within the main body of the gun. Similar to a bullpup weapon, although not quite that extreme.

Plus, although the gun is .75 caliber, thats still not such a huge round that the barrel length would be considered very short. There is still a good 1.5-2 feet of barrel length for a bolter, which is fairly close to what a modern sub-machine gun's barrel length is. And a bolter is an SMG.


All that extra space in the bolter isn't empty though. There is space for cooling system, targeting computers, combi-weapons, and a host of other nifty little do-dads that don't factor into table top play.

On a side note, those aren't 'exhaust holes' on the ma deuce, it's the jacket. But yeah, it's a heat vane for cooling the barrel.

 dementedwombat wrote:
Now I think of it I'm guessing most of the heat made by a traditional gun is friction of the bullet traveling down the barrel. After all it is always the barrel that gets hot and not the firing mechanism.

There's also the matter of each bullet being sent speeding away on a fast-expanding cloud of burning gas that has only one way to go. It's hot, very hot. And the chamber and such get hot too - that's what may cause a severely overheated gun to start cooking off ammo so it fires even if you let go of the trigger.

As I recall from my mandatory service the inner parts, especially the bolt head (containing the firing pin) could still be noticeably warm to the touch if we cleaned the guns immediately after target practice. And that was the Finnish Sako/Valmet licensed (and improved) AKM assault rifles fired on single-shot about 30 times maximum, not a machine gun throwing out several belts on the range.

Bolters were intended for use in a variety of atmospheres, including vacuum.
Under those conditions convective cooling is impossible and a radiative cooling system is probhibitively bulky. Instead the weapon uses its mass as a heat sink.

 Senden wrote:
Bolters were intended for use in a variety of atmospheres, including vacuum.
Under those conditions convective cooling is impossible and a radiative cooling system is probhibitively bulky. Instead the weapon uses its mass as a heat sink.

Not to mention - its pointed, rectangular shape makes it more resilient in vacuum conditions than, say, a cylinder or a rounded corner.

 Super Ready wrote:

 Senden wrote:
Bolters were intended for use in a variety of atmospheres, including vacuum.
Under those conditions convective cooling is impossible and a radiative cooling system is probhibitively bulky. Instead the weapon uses its mass as a heat sink.

Not to mention - its pointed, rectangular shape makes it more resilient in vacuum conditions than, say, a cylinder or a rounded corner.

Uhhh No, sharp angles cause higher stress concentration than smooth curves, its just much easier to make things out of flat sheets than try to form complex curved geometry

 Senden wrote:
Bolters were intended for use in a variety of atmospheres, including vacuum.
Under those conditions convective cooling is impossible and a radiative cooling system is probhibitively bulky. Instead the weapon uses its mass as a heat sink.

If left in a vacuum in deep space it will eventually radiate all its heat and sit at ambient conditions. Firing at that point would flash-heat the thing and cause it to explode, so the extra bulk may also include a heating system. The same would be true for ultra-cold world combat.

 Senden wrote:
Uhhh No, sharp angles cause higher stress concentration than smooth curves, its just much easier to make things out of flat sheets than try to form complex curved geometry

Not talking about stress specifically. I admit, I don't know the science behind it myself, but I am told by people who send things into space for a living that rounded objects are much harder to balance other factors like heat dissipation. Perhaps a better word I was looking for was "reliability".

Flinty wrote:Basically, GW weapon design tends to leave a lot to be desired from the technical point of view...

BrotherVord wrote:
Applying real world physics to a fictional weapon in a fictional universe isn't going to work. GW could easily just say that bolters of all kinds are made from a special alloy that won't melt at the heat produced by continuous fire.

Whilst I'm not in anyway having a go at you two, it does amaze me somewhat at the preconception that all of GW's weapons (and Tech for that matter) are mystical, magic gizmos. Obviously, aside from the huge weapons mounted on Titans and Starships, and the blatant arcane tech, most of GW's weapons and tech are either around now or are very close (10-20 years or so) to being a reality. For example, Plasma can already be generated and stored, the main factors limiting the creation of Plasma weaponry is simply projecting the plasma at a target (Plasma is the next state of matter after gas - ionised gas - and 'vents' much in the same way as a blowtorch does, creating a short, hot flame), and generating plasma with small reactors (Ideally fusion reactors, but we currently don't have those on a small enough scale). Similarly, Laser Weapons are already in development, and even in production in the case of the U.S Airforce's YAL-1 airbourne laser weapons system. Even power armour is gaining ground, although slowly due to the difficulty of finding a small power source and transferring power through joints. So, it still amazes me when people denounce GW's weapons/tech as pure 'magic', although I will accept that there are pure cases of WTF-ery

Grey Templar wrote:Plus, although the gun is .75 caliber

I was given to believe that Bolters and Bolt Pistols were .75 calibre, but Heavy Bolters were 1.00 calibre (30mm rounds). I could be wrong so please do correct me if so...

On the subject of Heavy Bolters, the whilst the barrel will eventually overheat/wear out, it isn't likely to be as common as on modern-day weapons or 40K autoguns, as, like stated above, the bolts are simply propelled down the barrel by a small charge, enough to ensure accuracy in a medium length barrel, however the rocket charge afterwards is the main propellant. Again, bolter rounds are very much a reality now. The Gyrojet weapons of the 1960's, whilst not being very accurate or better than conventional weapons, show that the concept is sound.

I agree that a lot of the stuff that allegedly powers 40k weapons is based on modern tech. I am more concerned that the weapons just won't work mechanically. Take the wrist mounted storm bolters for instance. In a lot of cases the model designer simply chopped the magazines off the bottom of the existing weapon and jammed them on the same side. Making that work mechanically would be a nightmare. With the macro calibre of most GW weapons the models would only be able to carry a few rounds, and then there is all the random rear part of the heavy bolter.

 Flinty wrote:
and then there is all the random rear part of the heavy bolter.

I'm telling you man, built in heat exchanger and gyroscopic stabilizer to counteract recoil.

It doesn't have to make sense, only be theoretically possible...

I'm an infantryman in the military and have fired the MK 19 automatic grenade launcher a few times. The makers of that weapon system are so confident it wont overheat they didn't even make the barrel removable. Since the rounds are mostly plastic they don't produce as much heat and the heat they do release is blown back and is key to the weapons operation. long story short, huge explosive bullets,(40mm which is larger then a heavy bolter round) high rate of fire, no overheating. Plus with a few extra pounds on the weapon itself and something to absorb the remaining recoil which is nothing a SM cant handle you have a recoiless automatic explosive ammo launching system that never overheats. That technology could be made tomorrow my friends. no sci-fi tricks necessary.

Weighs about 72 lbs. Make it more Boxy and add a hydraulic recoil suppression system. would weigh about 100 lbs what SM can't tote that around

Some information here:

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

Light on the materials tech, but it seems plausible.

I hope I'm not breaking any rules by posting the link. If I am, feel free to delete, infract, etc. "Blamming", however, is discouraged....

I'm guessing the fact that a heavy bolter is closer to a 20mm autocannon than a 12.7mm machine gun has something to do with it; compare the original poster's pictured Browning M2HB at 450-600rpm to an Oerlikon 20mm autocannon (a weapon from the same era) at 250rpm (figures from Wikipedia). Since it fires more powerful rounds it doesn't need to fire as quickly, therefore allowing it to build up heat more slowly and operate without as much cooling.

The other explanation, of course, is that there's an elaborate active cooling system in all that space in between the firing chamber and the rear of the gun on the heavy bolter.

 Warpig1815 wrote:

Grey Templar wrote:Plus, although the gun is .75 caliber

I was given to believe that Bolters and Bolt Pistols were .75 calibre, but Heavy Bolters were 1.00 calibre (30mm rounds). I could be wrong so please do correct me if so...

On the subject of Heavy Bolters, the whilst the barrel will eventually overheat/wear out, it isn't likely to be as common as on modern-day weapons or 40K autoguns, as, like stated above, the bolts are simply propelled down the barrel by a small charge, enough to ensure accuracy in a medium length barrel, however the rocket charge afterwards is the main propellant. Again, bolter rounds are very much a reality now. The Gyrojet weapons of the 1960's, whilst not being very accurate or better than conventional weapons, show that the concept is sound.

Yeah, I wasn't talking about a heavy bolter. I was talking about the standard bolter. But the HB is nothing more than a larger bolter, a still lethal charge to propel it out of the barrel like a normal bullet, complete with rifling, and then the rocket charge.

 Grey Templar wrote:

Yeah, I wasn't talking about a heavy bolter. I was talking about the standard bolter. But the HB is nothing more than a larger bolter, a still lethal charge to propel it out of the barrel like a normal bullet, complete with rifling, and then the rocket charge.

I thought bolters were smoothbores, relying on the propulsion of the round to spin-stabilize itself. But I went back and looked at the cut away view of a stormbolter from a few editions ago, and it points out that the barrel is rifled. Not as long as a modern barrel would be, but still, that's going to cause some heat.

Sure, and that must mean there is a cooling system built into the gun.

there is certainly room for one.

I believe the back of a heavy bolter is room for a crew of highly trained hamsters maintaining the weapon. Jokaero hamsters, probably.

I've always wondered why the bolter is depicted as having the receiver situated a significant distance above the actual breech of the weapon. This would indicate that the bolt is cycled from the magazine, up to the breech, as per a conventional round, but upon firing a further mechanism is then used to cycle the spent case further upwards to the point of it being ejected from the receiver. Now surely this last stage has no real purpose, as the round could simply be ejected straight from the breech as is usual, and would only serve to decrease the rate of fire due to the complexity of moving the spent casings around the bolter. I gather this is a prime example of GW's aesthetic value superseding real-life accuracy?

 Warpig1815 wrote:
I've always wondered why the bolter is depicted as having the receiver situated a significant distance above the actual breech of the weapon. This would indicate that the bolt is cycled from the magazine, up to the breech, as per a conventional round, but upon firing a further mechanism is then used to cycle the spent case further upwards to the point of it being ejected from the receiver. Now surely this last stage has no real purpose, as the round could simply be ejected straight from the breech as is usual, and would only serve to decrease the rate of fire due to the complexity of moving the spent casings around the bolter. I gather this is a prime example of GW's aesthetic value superseding real-life accuracy?

The bolt is obviously at the same level as the receiver, it just turns a corner inside the gun then turns back again to come out the barrel. Why do you think there's so much extra room in the gun height-wise.

I just solved it! The heavy bolter is so much bigger than it needs to be because the interior part of the barrel looks like one of those crazy straws.

Hahaha, I've just got images of some Space Marine stripping down an ork gun to find it just a box of metal bits, and then on the other side of the battlefield and ork stripping down a bolter to find a huge feth-off maze of barrels, cogs and other assorted .