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I have come across a number of lore references to Imperial weaponry that suggest they are considerably more powerful than similarly-sized equivalents today. This makes sense- the Imperium faces many monstrous foes that require considerable force to put down, and propellant technology has undoubtedly progressed in 30 millennia.

However, many of these hints and snippets suggest ludicrous levels of recoil if operating under conventional principles that would be unmanageable for an individual or vehicle using the weapon.

For example: Agripinaa pattern autoguns fire an 8.25mm bullet at ~820m/s. They are expected to fire in full auto too, although this is noted as being difficult to control. The listed example is only 6.2kg. Compare that to an FN Mag GPMG in 7.62mm NATO that is almost 12kg and fires a smaller-calibre bullet at a similar velocity. Yes, the 8.25mm calibre bullet could be weirdly shaped and oddly light, but the implication is that an autogun fires a big, fast bullet from a relatively light weapon and is on the edge of controllability in full auto.

Another example is Leman Russ battle cannons. Why does a 120mm smoothbore cannon with a low fire rate and ammunition capacity of 36 rounds need a bulky liquid-cooled shroud? You wouldn't expect sustained fire to be a major concern and modern tanks use similar cannon without water cooling. The implication is that the propellants used by Leman Russ are much more energetic, and that would come with signicantly greater recoil. Russes are not particularly massive tanks, and are very dirable and hard wearing. All of this suggests very advanced (by our standards) recoil dampeners to me.

I think bolt weapons give us a hint. The schematic for the storm bolter includes a "blast compensator", which is almost certainly a device for countering recoil:

Now, this is a Space Marine weapon, so will be very finely crafted. However it is reasonable to assume other bolt weapons include similar mechanisms to varying degrees of sophistication. Inertial dampeners are also found in many Naval applications, such as fighter/bomber pilot suits and assault ram harnesses. I think it is highly likely that similar tech is found in other Imperial weapons and allows them to fire much more powerful rounds and still be manageable by their users.

This tech may also be fairly easy to replicate, in the same way lasgun tech is highly advanced by our standards but commonplace in the 41st millennium and considered fairly simple and low tech.

It'd be worth making some research on how recoil dampeners actually becme better in real world. I couldn't say wither it'd be oil, mecanical parts, architecture that got better. Maybe materials?

 Maréchal des Logis Walter wrote:
It'd be worth making some research on how recoil dampeners actually becme better in real world. I couldn't say wither it'd be oil, mecanical parts, architecture that got better. Maybe materials?

Yeah, I agree a combination of material science and improved engineering. Imperial tech seems to be able to break conservation of momentum with inertial dampeners though, so all bets are off.

It may depend who’s carrying what.

Someone in Power or Terminator Armour may have that equipment deal with recoil, perhaps an automatic adjustment of arm positioning after every shot. Not stopping it entirely, because I understand that would stress the mechanics of the gun, because the energy of the kickback has to go somewhere. Maybe there’s a “pre-programmed” reaction to distribute the energy of the kickback in new and interesting ways, perhaps moving both arms to absorb it, without letting the barrel rise.

Autoguns? Presumably it’s at least whatever we use now

Lasguns? Well we still don’t have consensus on what they actually are. Coherent light, particle weapons? They could be entirely without recoil.

Melta weapons, being described as ranged microwaves may not have recoil at all, but require a very steady hand anyway to ensure the beam is properly focussed on one area.

Plasma? Who knows! I mean, I’m sure someone better versed in science will. But I’ve not a clue.

As noted in The other thread, Leman Russes operate outside normal earth climate ranges, and differential heating of barrels affects accuracy, so liquid cooling shroud has a range of beneficial uses.


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@MDG - you can easily design a gun to withstand recoil stresses. It’s even easier if the bearer is in strength enhancing armour, as the weight increase doesn’t really matter.

Bolter recoil never made much sense to me anyway, as having a bioropellant round means that the recoil can be much lighter. Just need enough to kick it out of the barrel, then The rocket motor smashes it up to terminal velocity. Yes you need enough oomph to enable damage at minimum range, but with an explosive round, you don’t need pure velocity for that.

On the space magic front, suspensors have been a thing since the dawn of Rogue Trader. Primarily noted to reduce mass on heavy weapons, but as soon as you can cancel mass, and/or control local gravity surely inertial recoil damping is not far behind.

What I'd bounce to following Doc's point: recoil dampeners in 40k 'eed not be integrated onto or into the gun itself.

They can fully be found in the armour or the platform the gun is operated in.

I'm also thinking cybernetics: individuals augmented with cybernetics might just get some form of additional recoil dampeners in them.

Besides, I'd say lasgun logically wouldn't habe got any recoil but that's cooler if it has got some

External recoil compensation tech is pretty common in the Imperium and integrated into lots of heavier armour. Even the Arbites have recoil gloves incorporated into their carapace IIRC

The simple answer is that GW writers don't understand guns and, in the case of the autogun example, definitely haven't done calculations to determine if what they're writing would be reasonable for a human to use.

Regarding the storm bolter illustration, the purpose for the "blast compensator" vents may depend on when it was drawn - and, at that point, whether the bolt round ignites within the weapon, or whether it is "fired" from the gun with it's gas (I think) primer, then the rocket motor kicks off.

Well, it also mentions piezo-electric ignition chamber, which I take to be for setting off the round.

 Dysartes wrote:
The simple answer is that GW writers don't understand guns and, in the case of the autogun example, definitely haven't done calculations to determine if what they're writing would be reasonable for a human to use.

Regarding the storm bolter illustration, the purpose for the "blast compensator" vents may depend on when it was drawn - and, at that point, whether the bolt round ignites within the weapon, or whether it is "fired" from the gun with it's gas (I think) primer, then the rocket motor kicks off.

Of course, at the end of the day "space magic".

Though if we imagine that the vents are huge, maybe they'd effectively be supposed to work like the open end of a rocket launcher, letting most gases loose of bolter round ignition make any, and thus cancelling recoil. Maybe?

 Maréchal des Logis Walter wrote:

 Dysartes wrote:
The simple answer is that GW writers don't understand guns and, in the case of the autogun example, definitely haven't done calculations to determine if what they're writing would be reasonable for a human to use.

Regarding the storm bolter illustration, the purpose for the "blast compensator" vents may depend on when it was drawn - and, at that point, whether the bolt round ignites within the weapon, or whether it is "fired" from the gun with it's gas (I think) primer, then the rocket motor kicks off.

Of course, at the end of the day "space magic".

Though if we imagine that the vents are huge, maybe they'd effectively be supposed to work like the open end of a rocket launcher, letting most gases loose of bolter round ignition make any, and thus cancelling recoil. Maybe?

I don't think they are vents (although they are shaped a bit like a radiator). Imagery and models look to have ridges but not vents at that location. My suspicion is some kind of miniaturised space magic inertial dampener to eat recoil.

I think the schematic is from 3rd edition, but I'd have to go digging to find the source.

Re. autoguns- I agree that is plausible, but equally firing huge, powerful rounds is a lot more necessary if you need to put down Orks than it is when fighting other humans in the 21st century. There is a strong rationale for infantry small arms to be powerful. In addition, we know lasguns hit hard, sometimes hard enough to take the limb off a human, and autoguns have broadly comparable effects. That requires some energetic rounds to be fired off. Given the technological disparity between even underhive mooks and our most advanced militaries (which makes sense with many millennia of time difference), widespread, accessible, comparatively low-tech* recoil dampeners that would make modern-day gunsmiths drool with excitement is not surprising. No one needs to understand how they actually function, just that if you build the doohickey in the right way and perform this rite after every 1000th cycle and the gun shoots much lighter.

*By 40k standards.

Edit: ooh, promoted to Commissar! Maybe I should buy that old Commissar I was looking at on eBay...

My respect, Commissar