so i want to know What organs or modifications are need for a biological creature to develop lethal force as a pooping machine gun.

something like how skunk spray their stinky odor as defense mechanism but more extreme that can launch many poop in extreme speed like machine gun.

(WARNING contain pooping link so if you cant withstand pooping/poop dont click the link)

something like this from cj7 movie but really lethal and can penetrate or dent bullet proof cuirass/breastplate, which unfortunately i cant found the precise number of safe distance between effectively dent or penetrate this plate armor outside of quite modest distance or close range, but that is against arquebus/musket gun generally so i dont know how devastating machine gun with lead shot bullet is.

  • the plate armor dimension is: H. as mounted 54 in. (137.2 cm); Wt. 86 lb. 8 oz. (39.24 kg). (theres many diverse bulletproof plate armor with different weight and thickness, but this is the one i can found and has image proof of it)


enter image description here

  • the poop is round like rabbit poop or lead shot bullet of early gun bullet, the size is 5 mm to 10 mm and can produce 200-300 poop a day, the density is like rabbit poop (i cant found the precise number, but generally this is what i get from rabbit poop)

  • they can control the force so they can poop without lethal force if they want to.

  • generally the creature size is around rabbit size to common dog or goat size but i dont mind the disproportion between each body parts especially the rear part to be able to make this ability/defence mechanism possible.

  • i dont think about the diet specifically yet but generally they either a herbivore or omnivore.

  • generally i was thinking to make my civilization to use them as natural/organic gun weapon, so would help alot to explain how to externally trigger it too.

  • please include the math since iam not good with math, and i am not knowledgeable about gun especially modern gun.

and feel free to edit my grammar or tag to the appropriate one, since i am not sure about the tag is appropriate for my question or not.

  • 4
    $\begingroup$ For those downvoting, the question might be weird but it is technically sound even if the answer turns out to be "no this isnt biologically feasible". $\endgroup$
    – Demigan
    Commented Mar 10, 2020 at 9:07

1 Answer 1


TL;DR: the mechanical issues of a biological gun would be very, very difficult to overcome. If they were overcome, the energetic costs of firing sufficiently large projectiles at sufficient speeds would be punishing.

This doesn't seem to be impossible, especially for a deliberately engineered species, but it is implausible that such a thing would evolve naturally.

The problem you'll have is making somthing that can withstand the chamber pressure required to fire the projectile at deadly speed without traumatic failure.

A musket or powerful air rifle like a Girandoni might have a chamber pressure of the order of several megapascals (7Mpa = 1000psi, for those of you engaging in a little historical re-enactment). In order to withstand the forces of firing, the chamber will need to be made of something like bone (whose maxiumum compressive strength is of the order of a hunderd MPa) so as not to burst immediately.

The next problem is of course that the energy released in firing is done over a very short time, meaning that the amount of power developed is very high. You could make a bond gas bottle to survive that pressure, but the heat and shock of rapid compression and decompression is likely to cause damage to the bone... microcracks initially, but those cracks will expand and propagate on successive shots until the chamber fails. You'll therefore need to have some sort of regenerative tissue on the inside of the chamber, perhaps something that extrudes keratin to provide a less strong but more tough lining that is expended and replaced over time. The problem you have then is to provide a blood supply to the cells that produce the liner in such a way that it cannot be damaged or destroyed by firing pressures, or form blood clots even if the vessels themselves survive intact.

Now you need a loading mechanism. You're implying a breech loading mechanism rather than a muzzle loader, and that substantially complicated things. A regular sphincter clearly isn't going to be adequate here... instead, some sort of bony plug will be required to be slotting and locked into place before each firing. The seal will have to be near perfect, because backblast could easily prove fatal. Maintaining that perfect seal whilst simultaneously allowing the passage of solid, liquid and gaseous waste of various textures and compositions will be extremely challenging. The same regenerative liner system will also be needed for the breech as for the chamber (and barrel), but it will be slightly more complex given the need for perfect sealing on a mechanism that can be opened and closed.

Making the opening and closing mechanism robust to mechanical issues is also likely to be tricky... constipation could jam the breech closed, resulting in a fatal bowel obstruction. Having a solid chamber and barrel is also likely to make regular defacation more awkward, and represents a possible future route of infection or parasitism.

The mechanism of generating sufficient pressure to propel a projectile isn't really worth going into here... suffice to say that it does appear to be possible to do so biologically (given the existence of the bombardier beetle). Being able to generate enough propellant is going to be extremely energetically intensive, however. Musket balls had muzzle energies of the order of a few kilojoules (a Brown Bess musket developed about 3-4kJ, for example). Assuming propellant can be manufactured with an efficiency equivalent to human mechanical efficiency (which is ~20%), and assuming a gun efficiency equivalent to a modern rifle (which converts about ~30% of the combustion energy to kinetic energy of the projectile) you'd need an intake of 50-70kJ of food per shot (and the efficiencies of your meat-gun are likely to be lower than a modern precision-machined rifle!). This might not sound like much when a human diet might bring in aout 8000-9000kJ (of which about 25% is available for things other than merely staying alive and intact) but it is approaching the amount of energy expended by a human to sprint 100m. Something the size of a bunny or dog could use that energy to travel much further, or fight harder. For a predator, your gun seems energetically worse than ambushing. For prey, the gun would be potentially ineffective against ambush (including aerial predators, not merely things that hide in bushes), and definitely ineffective against multiple predators.

Certainly the gun would not be a machinegun, given the amount of energy required to make repeated shots in a short period of time, let alone the associated wear and tear on the structure of the gun. Shots would be infrequent. This does at least make the engineering requirements of the gun a little simpler, as time can be taken between shots to heal and repair.

Given that grazing species must already eat and ruminate (or re-eat, in the case of bunnies) more or less continuously to keep up with their body's demands, given the relative lack of nutrition in their food, it seems unlikely that herbivores will be able to power a gun like this. Omnivorousness seems a requirement, with as much animal protein and fat as possible. A gun wielding predator seems a possibility, though aiming might be difficult.

Oh, and as a final problem, you have this requirement:

The poop is round like rabbit poop or lead shot bullet of early gun bullet, the size is 5 mm to 10 mm and can produce 200-300 poop a day, the density is like rabbit poop

That is far too low density... your projectiles will be too light, and too soft. Rabbit poop is basically compressed grass, and there's no way you'll be able to fire it fast enough to kill, especially in those quantities. Even a naked human would be unlikely to suffer harm from high-velocity rabbit droppings, unless perhaps struck in the eye (and even then that wouldn't be fatal). Armoured humans might not even notice.

You'll need your animals to consume small stones to use as ammunition. They might be stored in something like a crop, but at the other end to normal.

200-300 shots a day would require energy equivalent to running most of a marathon, not inculding wear and tear on the firing mechanism.

  • 2
    $\begingroup$ A normal human diet brings in about 8-9kJ Correction needed: a google search tells the average human diet is 8700kJ. Even if it may seem affordable from this PoV, I'm personally not inclined to poop 200-300 Brown Bess musket bullets/day ;p $\endgroup$ Commented Mar 10, 2020 at 11:30
  • $\begingroup$ what about the speed of water jet ? are water more dense than compressed grass ? or what the force math to make this rabbit poop dense deadly ? even if it out of reality scope, i just want to know the math. $\endgroup$
    – Li Jun
    Commented Mar 10, 2020 at 11:34
  • 2
    $\begingroup$ @LiJun Given that water jet cutting uses 2000 - 6000 atm jets of water mixed with abrasive powders and dispensed quite closely to the target , I think is safe to assume you can forget about it. Perspective: the pressure at the bottom of the Mariana trench is around 1100 atm. $\endgroup$ Commented Mar 10, 2020 at 11:44
  • 2
    $\begingroup$ @LiJun water jets have an extremely limited range in air, as air resistance breaks up the jet. That is why water jet cutting tends to be done with a device in contact with the material. If you have to sit on something to poop it to death, you may as well just use claws and teeth and muscles and not muck about with pointlessly complex and potentially suicidal bio-re-engineering. If you meant water as a propellant for some projectile, don't bother... it would be rubbish. $\endgroup$ Commented Mar 10, 2020 at 13:21
  • 1
    $\begingroup$ @AdrianColomitchi close enough to with a few orders of magnitude <cough>. $\endgroup$ Commented Mar 10, 2020 at 13:22

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