# Can guns be rendered unusable by changing the atmosphere?

I have an idea for a story in a post-apocalyptic setting where guns and other explosive devices unusable or otherwise impractical.

Is it possible to do this by changing the atmosphere (either by adding, removing, or changing the proportions of the chemicals that make up the standard earth atmosphere)?

The resulting atmosphere must be capable of supporting life, although it would be acceptable if human life required artificial support (e.g. portable supplementary oxygen supplies). Ideally, I would like to avoid removing oxygen completely; instead I want to change the environment the minimum amount to prevent combustion.

• When you say "prevent combustion" do you mean no fires can sustain themselves anymore? That's a lot more than just guns. – Schwern Nov 18 '16 at 3:17
• There was an Australian author I read a few decades ago who had nearly exactly that as a plot line. I can't remember for the life of me his name, Jack something I think. Giant space-battleships circled Earth and enforced it, I think, rather than actually changing the world. And maybe it was electronics and not gunpowder, actually, hrm. – Joe Nov 18 '16 at 4:16
• @Joe: You may be thinking of Sean McMullen, either his "Souls in the Great Machine" (1999) or "The Miocene Arrow" (2000) or "Eyes of the Calculor" (2001). Novels in the Greatwinter sequence. – a4android Nov 18 '16 at 6:31
• Modern guns work in the vacuum of space... In theory at least. All The energy and reaction material is inside the brash cartridge. If the atmosphere were thicker, that would mitigate guns. Bullet do poorly in a swimming pool. – Sqeaky Nov 19 '16 at 4:36
• Non-science: Dies the Fire ("spirits did it"). Sorta Science based: John Ringo's There Will be Dragons - energy transfer net takes energy from everything above a certain level. – Clockwork-Muse Nov 19 '16 at 5:33

Make the atmosphere more combustible by adding lots of methane or other super-volatile gases. It won't stop the guns from functioning, but it will make using them suicidal for the wielder.

It does not even have to be super volatile gasses (as the presence of such might prevent human to walk around without life support systems), it is enough to increase the oxygen concentration to slightly over 30% to make it quite dangerous to fire rounds. If the atmospheric oxygen concentration is over 30%, then even wet plants will ignite and burn if there is anything to light them on fire, yet humans and animals will not be in any danger from breathing it (it will even slightly enhance performance when using your muscles). As a bonus, you will also get giant insects as their size limit is a function of how well oxygen can diffuse in to their bodies.

• This is not dissimilar to the Frank Herbert "mutual annihilation" interaction of lazguns and personal body shields. Basically if a lazgun hits a personal shield, it will annihilate both shooter and victim. And because lazguns protect from projectile and small explosive weapons, it forces combat to be largely hand to hand bladed combat. – Stephen Nov 18 '16 at 3:28
• If you are trying to be scientifically accurate then an atmosphere that is a combustible mixture is a non-starter. Even in the absence of sources of ignition such as lightning, easily oxidized gases will oxidize slowly, but I think on a timescale of weeks. An atmosphere stable enough to count as an atmosphere can't be so unstable that it can be ignited by a gunshot. ... But what if there are widespread massive leaks of odorless explosive gases from underground? You'd never know if it was safe to strike a match. Hmm. Henry may have something. – Mark Foskey Nov 18 '16 at 3:39
• @MarkFoskey "An atmosphere stable enough to count as an atmosphere can't be so unstable that it can be ignited by a gunshot." Not true! In fact, the earth itself was like this during the Carboniferous period: en.wikipedia.org/wiki/Carboniferous#Rocks_and_coal – Shadow503 Nov 18 '16 at 12:17
• "As a bonus, you will also get giant insects as their size limit is a function of how well oxygen can diffuse in to their bodies." -- For certain definitions of the word "bonus" :P – Steve-O Nov 18 '16 at 15:16
• What, @Steve-O, you're not looking forward to riding a giant cockroach to work?? – Wayne Werner Nov 21 '16 at 13:29

Considering the propellant in all munitions that I'm aware of (except fuel-air bombs and spud guns) is self-oxidising, that is to say, it requires nothing from the atmosphere (guns and bombs work fine underwater or even in space - well... they work fine once anyway) I'm inclined to say that, other than some kind of corrosive atmosphere eating the shells, that there's probably not much you can do about atmospherically preventing munitions from functioning.

However, as combustion engines are dependent on the atmosphere to run (they get their oxidiser - oxygen - from the air) so there is probably something you could do to stop the engines, maybe something that causes them to gum up or something that makes them rust really fast (really salty sea air works well)

• Automatic and semi-automatic guns will fire underwater, but they typically won't cycle the next round into the chamber. Air that's dense or viscous enough to make that happen wouldn't be breathable, though. – Peter Cordes Nov 18 '16 at 5:30
• And forgot to mention, even that wouldn't defeat a revolver. A revolver uses the movement of the trigger to rotate the mechanism, not force from exhaust gases. – Peter Cordes Nov 18 '16 at 8:29
• @PeterCordes Yeah, I should probably mention that shouldn't I, range would be terrible too, 2 meters max before the bullet falls to the floor (thanks Mythbusters) – Samwise Nov 18 '16 at 20:01
• Really really salty air doesn't stop engines (at least not in the short term), or marine engines would not exist. – Johnny Nov 19 '16 at 0:10
• @Daerdemandt 60m is current See supercavitating. But thats still pretty shitty overall. – Angelo Fuchs Nov 21 '16 at 12:56

If you are willing to go for a bit of hand waving: There are nanoparticles in the air that makes it act like a non-Newtonian fluid, or oobleck.

Usually, the nanoparticles float around completely unnoticed, like dust. But if something starts moving very quickly, the air around it seems to solidify, destroying and stopping the object. Then the air quickly reverts to normal. Maybe it kicks in at high speed, near the speed of sound. This would make guns infeasible. You could also make it depend on acceleration instead - this would still allow high speed vehicles or planes in the affected air, but still rule out guns. It might also have an effect on arrows. Just make sure people don't get killed when they sneeze.

I imagine the way it works is that the nanoparticles are tiny electronic floaters, like large molecules or nanoscale transcievers. They have a kind of electric field between them. If one starts to move rapidly between the others, they induce some power in the particle - like if you move a conductor through an electric field. This in turn causes the particles to attract each other. But if they come closer together, they also repel each other - the result is that they quickly form a long range lattice or crystal. The surrounding air is also locked into the lattice, via an interaction between the activated particles and the air molecues. Either something like static electricity, or a long-range version of Van der Waals-force. The result is that the viscosity rises quickly, and the air becomes very thick or even solid.

Note that my explanation how it works uses a lot of "kind of" and "something like" and is total BS :-). So you'd need to be comfortable with "nanotechnology as magic", or work a bit on the science of it first.

• Everyone will have pulmonary fibrosis. Everyone. – DOS4004 Nov 18 '16 at 8:36
• Well then, aehm, break out the portable oxygen supplies :-) – jdm Nov 18 '16 at 9:20
• @DOS4004 How long would one go breathing without a filter to get 50% chance of getting pulmonary fibrosis? If something reasonable, it can be turned from obstacle to flavour. – Daerdemandt Nov 18 '16 at 21:49
• Probably on the order of years (everyone over 20 who never wore a filter would probably have it). It depends on the concentration, but sawdust might be similar. – DOS4004 Nov 18 '16 at 22:29
• I think this one is the coolest idea on the page. As a bonus, everyone gets a little bit more iron in their diet. I feel like you could handwave the pulmonary fibrosis pretty easily, maybe people have nanoparticle immune systems from before the collapse or something. – Azor Ahai Nov 18 '16 at 23:18

if its post-apocalyptic you can just be truthful and have making the bullets difficult. Making modern propellants is not something you can do at home, especially the primer. reloading bullets is based on being able to buy these materials. Using black powder (which you can make) in modern firearms, will gum them up rather quickly.
preventing the making of explosives is much more tricky. basically you might want to look at a different way to disable firearms than changing the atmo, since life still basically runs off of really slow combustion of carbon, so any change that prevents one will prevent the other.

• Actually hand casting bullets is still practiced. Current modern firearms like the 38 special actually started as black powder weapons. As indicated, black powder can be made. Actually, nitropowder can also be made though with significant danger and expertise needed. The main problem is the primer. There are examples of even those being made by insurgents. – Blackbeagle Nov 18 '16 at 2:16
• primers made from other manufactured goods, like matches, which would be even rarer in a post-apocalyptic setting. but you are right there are some modern firearms that can handle black powder, but most will not, especially anything semi to fully automatic.The bullet and casing are easy, propellant and primer are the hard parts. – John Nov 18 '16 at 18:16
• so back to flintlock muskets (most black powder still rely on external primers) but you won't see many modern firearms for very long. How post, post-apocalyptic are we talking. – John Nov 18 '16 at 18:29
• @John How post, post-apocalyptic are we talking A span of time no more than 2 to 3 decades after the Event. – Beofett Nov 18 '16 at 18:56
• @Blackbeagle Production of guncotton doesn't require chemistry higher than they teach at schools. Access to materials and equipment would be needed, though, to produce batches of consistent qualities (vital for accuracy). Primer would be a problem indeed, but that still is not that bad. College-level knowledge of chemistry would probably suffice to produce something safe enough. – Daerdemandt Nov 18 '16 at 21:10

Since most explosives don't even need an atmosphere (you can fire guns under the water), it must a special atmosphere that is actively preventing explosions of all sorts. You could make the atmosphere to have higher density and higher viscosity. A fancier atmosphere would be one laced with super-nanobots that dissipate all motion energy to heat quickly, sort of like reverse-Maxwell's daemon.

• That sounds potentially problematic for the inhabitants too, heavy thick air being hard (and tiring) to breathe – Samwise Nov 17 '16 at 21:28
• @Sam: you'd just need different lungs, at some point they'd be more like gills. – Michael Borgwardt Nov 18 '16 at 8:34
• Water is vastly denser and vastly more viscous than air but, as you say, guns still fire underwater. So exactly how dense and viscous are you proposing to make your atmosphere? Of course, a dense, viscous atmosphere will vastly reduce the range at which bullets are effective. However, it will make explosives much more dangerous because the shockwaves travel more effectively in the denser medium. – David Richerby Nov 18 '16 at 17:17

# Reduce medium range visibility

A typical way to reduce the usability of ranged weapons in general, and thus guns, is by ensuring that there is no clear line of sight from attacker to target.

This can be achieved in numerous ways, some more, some less realistic.

### Fun solution: Weird visibility

Rather than making people invisible, let the air have a highly variable refraction index. This means you can see enemies all around you, but that you just can't point out exactly where they are. Never mind shooting them from a normal range. As a result, people may find a knife on a chain to become a more efficient weapon than a gun.

### Realistic solution: Low visibility

Make sure that, you can't see very far. There is simply so much smog that one can just see who is walking in front of you. Once the average range of an encounter becomes small enough, people will go for swords and the like to maximize their killing potential.

Note that if these conditions were to be so extreme that gun usage would drop to near zero just because of them, there would be a significant impact on daily life as well. If you are just interested in disabling distance shots the impact on daily life could be fairly minimal.

Cartridges are essentially self-contained and (can be) environmentally sealed objects, very durable in every way (compared to humans or vehicles). Nothing in the atmosphere is going to stop a cartridge from going off when primer is hit right.

A basic gun is also so simple, just barrel to contain the explosion, a lock to keep the cartridge in place, and a mechanism for a hammer to hit the primer, that nothing in atmosphere is going to prevent that from happening. Even some complex guns, such as the iconic AK47, are very robust. Tough conditions just need looser tolerances, which reduce power and accuracy, but even the most loose, but otherwise well designed gun is still going to be superior to any more primitive kintetic weapon in almost every way.

Doing "magic" with atmosphere which limits maximum velocity (like that non-newtonian fluid answer) would make existing weapons ineffective, but new ones would be rapidly designed and produced, which would fire heavier projectile with lower speed.

If you made explosive atmosphere, you would get gun designs which would cool down the explosive gasses so that they wouldn't trigger atmospheric explosion, or you would get remotely operated guns which would not be harmed by a little local atmospheric flash. Or just blast shield around the muzzle for very local flash. Or whatever. In any kind of stable (think of lightning and volcanoes) atmosphere, there's a way.

Basically, if you can shoot arrows/bolts, or just throw spears, you can make a gunpowder version, which will fire bigger projectiles more rapidly, with optimal velocity, more accurately, without it tiring you or requiring long training. The gun models we have on Earth today are optimized for our conditions, different conditions would result in different designs. But the basic advantage, the energy stored in the gunpowder, turned into kinetic energy of projectile with a twitch of a finger, "point-and-shoot", you can't hand-wave that away. If you threw modern humans with now-unuseful guns and lots of ammo into alien environmemt, they'd open the cartridges, repack them, and create ad-hoc "guns" working in that environment.

• This should be the right answer. So long as we can isolate Oxidizers and reducers, there will be booms. – tuskiomi Nov 21 '16 at 18:10

Aside from the explosive atmosphere answer, having the atmosphere be the thing that prevents firearm usage is rather implausible. If the story allows it, I would say use other factors, such as a combination of history, manufacturing practices, and technology!.

Even if a single factor is unlikely to eliminate firearms and explosives, the combination of multiple factors makes it so impractical/dangerous that none would be used in favor of other weapons

1. Technology. This one might be a major leap culturally, but technologically it's entirely possible. Consider the worldwide weapons ban mentioned below and add in a dash of government that (at least in the area your story takes place) implemented heavy Live Fire Detection Systems, which detect and respond to gunshots and/or explosions. Though the Geneva convention currently prohibits computers targeting and engaging (i.e. shooting at) humans without another human pulling some sort of trigger, I'm guessing the events leading up to the apocalypse threw that out the window. Combine aforementioned LFDS with advances in self-sustaining aircraft and laser weaponry, and a sky full of drones that fry anyone that fires a bullet is entirely possible. The kinda scary thing is that it's possible today, it would just be expensive before the systems enjoyed the economies of scale of mass production. South Korea's border already has a gun deployed that can auto-kill a human from 3 kilometers away, and that tech isn't even cutting edge!

2. History - Consider that there is first a worldwide gun ban similar to Australia's ban, which massively reduces the number of guns in the world by physically destroying them. After a subsequent worldwide ground conflict and a sufficient amount of time, most modern ammunition may be spent. Not 100% foolproof on its own, but making guns and ammunition rare adds to the other factors. Some regions of the world (like yours, perhaps) would likely be gun-free altogether.

3. Manufacturing - In a post-apocalyptic world, it can be assumed mass manufacturing is no longer possible. Modern ammunition was not produced until the mid-to-late-1800s, and neither were interchangeable parts (such as barrels, magazines, revolver cylinders, etc.). Before then, projectiles and powder were loaded into guns separately. They didn't have nearly the range or accuracy, were much heavier, and reloading was extremely slow. Practical for large-scale firing lines between standing armies, not so much for any other purpose... unless you only want one single, fairly low-accuracy shot. You can safely assume modern firearms are impossible to recreate in such a world, and who would risk a crappy musket shot when there are flying death lasers everywhere?

4. Add in pockets or "springs" of explosive gasses leaking from underground from the explosive atmosphere answer. Why not? I think it's a good idea, and credit where it is due!

All ordinary explosives are self-contained, they work totally independently of the atmosphere. Thus the only way you can stop explosives from working with atmosphere is to have an atmospheric pressure above the detonation pressure of the explosive. At that point when you set them off they'll get bigger because they're warmer but that's it. The highest detonation pressure I can find is about half a million atmospheres.

Unfortunately for your story such atmospheres are not compatible with human life. Everything becomes toxic long before this sort of pressure is reached.

Maybe up the humidity - a lot.

A wetter, more humid atmosphere would make it harder for things to burn, and harder to ignite. It would take more to start a spark, and more to make that spark catch something else afire. A wetter atmosphere might have prevented the rise of firearms, as earlier versions wouldn't light when the air or accelerator was damp.

Of course, modern firearms are designed not to be so vulnerable to environmental conditions, they should be able to go off even under wet conditions. That's sort of not the point.

However my point was less about firearms and more about manufacturing. Accelerates might be designed to work independently of the atmosphere, but they have to be carefully manufactured, controlling many variables, to even get to that point. So, if the gunpowder manufacturing plant has a hard time keeping itself dry, we can see how well bullets work packed with damp powder (or how well they don't). Heat might help dry things, but there's a limit - and it can be pretty energy intensive. Or dangerous, given you're working with explosives to begin with.

Of course, there will be ways to make explosives and bullets work anyway - climate control on that level takes a lot of tech but it's doable - but they will be a lot more difficult and expensive, which might be enough to make them unpopular, or put them out of price reach for average gangs. And the tech involved (heaters, air conditioners, dehumidifiers), might be difficult to produce or maintain in a collapsed society, without a solid tech base behind it, especially since the individual skills would likely have been let lapse as luxuries, until they realized the secondary effects on manufacturing stuff like gunpowder.

• For reference, getting gunpowder slightly damp actually increases its power until you get it so wet it won't light. Water is very good at soaking up heat and turning it into pressure (hence why we build steam engines). An excessively damp environment could still cause manufacturing issues like you suggest though. – Perkins Nov 21 '16 at 19:19
• @Perkins - ooh, neat, I didn't know that. I was assuming wet enough to have trouble lighting, it's true. Although even being more powerful an explosive might be its own kind of problem, if the gun in question isn't equipped for the extra explosive power in its bullets and that causes other problems - maybe it can be one more reason for guns to be dropped as unreliable in this world. – Megha Nov 21 '16 at 19:33
• It could be an issue. Although most guns will have enough of a safety margin to be able to handle it. I've seen powder hammers malfunction due to the extra pressure from old cartridges that had been stored in a damp environment though, and some semi-automatic weapons don't cycle correctly unless the amount of power in the round is almost exactly right. – Perkins Nov 21 '16 at 19:43

If the atmosphere is thick enough, the projectiles fired will just slow down from friction very rapidly and end up falling to the ground harmlessly shortly after leaving the barrel.
Can still use the gun at short range, say a pistol at near contact range, but at longer ranges they'll be all but useless.

A bigger question is how to explain a massive increase in air pressure as having been caused by your apocalyptic event.
And of course building a world where such an extremely dense atmosphere (it'd have to be just about liquid) can exist and your creatures survive in it who previously survived in a far less dense atmosphere. The atmospheric pressure would be immense, and their bodies probably incapable in dealing.

You would need to have some kind of electrical/static field in the air that would penetrate the bullet casing causing the gun power to ignite prematurely. Even just building a bullet, it would explode seconds later.

I believe Memming gave an awesome idea about nano-bots, buts it gets problematic with motion-preventing, affecting everything that moves. My idea would be nanobots infesting the atmosphere in a way that they sense gunpowder or other explosives (extremely sensive AI-like bots) and render all encasings and shells unusable, entering ammunition and changing propelents and explosives structure at molecular level etc. Well, this approach depends on how high-tech and Sci-Fi-ish you wanna get.

Invent some molecules, able to quickly stick to iron (or whatever metals gunbarrels can be made of) and create thin film on it. (These molecules probably must not cause harm to most plants and animals.)

Then, two possibilities. If such film is thick and hard enough, then shooting will be problematic, gun may explode or bullet speed will be very low. If it is not, then it may change its properties after exposing to high pressure and/or temperature and for example bind enough something from atmosphere after shooting and making guns unusable again.

• Just coat your moving parts in tin or copper then. Or even plastic. Keep the iron inside for strength. – Perkins Nov 21 '16 at 19:21
• I rather thought about reusing existing guns - sure you can find some new material, resistant to my 'corrosion' and suitable for guns. – Arvo Nov 21 '16 at 19:25
• Copper plating could be added to existing, simple guns with a minimum of effort. There are even ones currently being manufactured with various kinds of metal or plastic coatings to prevent corrosion when they get carried in someone's sweaty shoulder holster all day. Your idea has some merit, it just needs a bit of expansion and tweaking. – Perkins Nov 21 '16 at 19:51

One alternative way at coming at it which might suit an apocalyptic scenario would be the occurrence of a universal and severe allergic reaction to explosives. It would make making ammunition very difficult in a technologically regressed world, while firing a weapon would be virtually suicidal (as the residue would spread through a fair amount of the local atmosphere)

As other posters noted explosives often work totally independently of the atmosphere since they contain everything needed to explode.

How about making explosives much more sensitive because of some sort of radiation. If this radiation is present globally (atmosphere with radioactive particles for example) it would make really hard to create and carry explosives safely. While local radiation would prevent use of explosives in critical areas because they would explode on borders of radiated area.

Local radiation could be also from atmosphere or from some radiation generator. Radiation should be harmless to life, like electromagnetic waves that are all around us.

• It's hard to imagine how this radiation would make explosions more sensitive without also making, e.g., the sugar molecules within your body much more willing to decompose. – David Richerby Nov 21 '16 at 9:12
• True, but we are bombarded daily by many types of particles, some of them stop immediatelly while some go through earth without notice, all of them have some kind of impact already, so there is possibility to find one. – Piro says Reinstate Monica Nov 25 '16 at 10:31
• I don't understand how your response relates to my comment. Your body and explosions both work in essentially the same way: they involve chemical reactions that need a small amount of energy to trigger them and, once that's happened, the reaction releases more energy than you just put in. How do you propose to make the chemical reactions of guncotton (chemically, essentially sugar plus nitro groups) much more sensitive without also making the chemical reactions in my body (essentially, sugar minus nitro groups) not also go haywire? – David Richerby Nov 25 '16 at 10:39
• And how is this mechanism going to deal with the explosives that don't look like nitrated sugars, such as nitroglycerine (essentially nitrated alcohol), TNT (nitrated paint thinner), RDX (which doesn't fit in to the pattern of "essentially something you're familiar with, plus nitro groups"), gunpowder (essentially coal plus an oxidizer), ... – David Richerby Nov 25 '16 at 10:46
• Well it is up to OP to present it in a way to make any sense. I am not a chemist to reason about it deeper. I just think that since radiation has no problem to go through explosive material and shell casings it is more plausible than other solutions since explosives work independently from atmosphere. But your points are valid – Piro says Reinstate Monica Nov 25 '16 at 11:20

Perhaps a chemical could be added to make the atmosphere a non-Newtonian fluid (like oobleck, except a gas). This make it difficult to exert force on the air around you, maybe not enough to make running hard.

the most obvious effect will be that bullets, with incredibly high velocity, will slow and fall to ground much quicker.

I think this may also mean that vibrations in the air will be dampened, such to reduce the effects of an explosion. It may also make shouting or producing loud sounds difficult.

• Wouldn't a non-Newtonian atmosphere make explosions more powerful? Water (more viscous) transmits shock waves much better than air (less viscous). – David Richerby Nov 21 '16 at 9:11
• Thats a good question, and I don't exactly know the answer, but my instinct would tell me, that non-Newtonian fluids behave solid, and solids usually dampen explosives. at the very least, shrapnel would be slowed just as a bullet would. – redbow_kimee Nov 29 '16 at 1:43

## Weather

Some other answers suggest adding humidity to prevent combustion. This is a terrible idea, as has been stated. However, it could work for a different reason, especially if we add some sand.

### Firearms can be unreliable

Or, at least, the modern version, with high effective ranges and fancy concepts such as "semi-automation". More simple weapons aren't quite, though.

The most basic version of a gun (as we think of it) is as follows:

• Take a projectile.
• Stick it in a fireproof tube.
• Make an explosion that launches the projectile out of the tube at a high velocity.

This can be an improvement over bows and the likes at very short ranges, if your goal is piercing armor, but it's very unreliable at longer ranges. Guns of this sort have been around since around the 1100s, and the basic gist of it wasn't drastically improved upon until around the 1850s or so. They were mostly used for armor-piercing purposes and due to needing much, much, much less training to use effectively than a bow at similar ranges. However, they were exceedingly inaccurate and took long to load.

These would still be viable, but only due to simplicity... and even then, only to an extent. Though, I suppose the title of this subsection is somewhat innacurate...

### MODERN firearms can be unreliable.

One of the more popular handguns in pop culture is the Desert Eagle. While it may look cool and sound nice, it's really a terrible weapon. It's incredibly heavy (making it hard to hold steady for aiming), and jams exceedingly frequently, especially in humid or sandy areas (ironically making it useless in deserts). Despite all that, it's also WAY more expensive than most other guns (just under \$2000 USD) - you can buy actual, military-grade, melt-through-steel-in-an-instant laser weapons for around that price.

Most firearms are, to an extent, similar, anymore.

Guns, these days, are astoundingly intricate. If I tell you to go make a .44 Magnum, you wouldn't be able to. If I went to someone who regularly machines things as a hobby and told them to make one, they wouldn't be able to either. Only a huge assembly process specifically created for the production of .44 Magnums would be able to make one with any efficiency, because there's just so many tiny parts that all need to be perfect to even get off one shot.

As such, even if I already have an assembled, working .44 Magnum, it can still have issues firing if it gets full of sand or starts to rust or the likes. And a good, old-fashioned revolver is one of the most reliable weapons you can own - just imagine what it's like for even more complex weapons with 35 extra parts for feeding an ammo belt and another 12 for ejecting spent cartridges, 17 for feeding in new bullets from a clip, et cetera.

### Let's just get to the point already

Now imagine some incredibly-humid, sandy-as-all-getout land where so much action goes on that you'd never be able to sit down and do maintenance even half as often as you should under good conditions. Within ten years, nearly all complex firearms would be so rusted and ruined that they could never fire a single bullet again.

Now, as for explosives...

### There's just no stopping explosives

A bomb is even more simple than a gun.

• Get something that can explode
• There is no step two

People make bombs with a quarter-cup of laundry detergent, an empty milk jug, a piece of flint and some metal to hit it against. These are effective enough to be as costly to troops fighting in a war than the actual "fighting in a war" bit. Making the air more wet isn't going to stop it. Making the air amplify that explosion just makes it an even MORE attractive option! There's just no stopping bombs without deoxygenating the atmosphere. Sorry.

• I think "most firearms" today is still AK47 and its clones. Rather reliable, rather easy to make, due to rather loose tolerances. Yet also not too inaccurate. – hyde Nov 19 '16 at 20:29
• [citation needed] for the claim that there are cheap, effective laser weapons in the world today. And you seem to misunderstand explosives: explosives don't require atmospheric oxygen. Old fashioned explosives such as gunpowder already contain oxidizers; modern explosives (TNT, nitroglycerine, C4, anything) contain everything you need within a single molecule. – David Richerby Nov 21 '16 at 9:09
• Building a working, .44 magnum revolver would only require machining tolerances of about 1/1000 of an inch. Anyone who can't achieve that doesn't deserve to call themselves a metalworker. Good metalworkers have been able to do it since the middle ages. I have successfully made replacement gun parts with nothing more than a piece of steel, a hacksaw, and a good file. It's a slow, tedious process, but there's nothing magic about it. Designing a working revolver from scratch would be slightly more challenging, but anyone who can build a model steam engine could do it with a bit of effort. – Perkins Nov 21 '16 at 19:32
• @DavidRicherby Yeah, I tried to find a good citation, but I can't exactly remember where. Honestly, I read about it in a Cracked article. If it bugs you too much, I can remove it. – Papayaman1000 Nov 21 '16 at 20:02
• @Perkins Yeah, I'm aware deoxygenation won't stop explosives definitively. I'm just saying, there's no stopping them. I just tried to put that into perspective. As for the .44, well, I suppose you make a good point. We are talking about the post-apocalypse here, though, so who's to say there's the necessary skills and tools among the world's denizens? – Papayaman1000 Nov 21 '16 at 20:16

I also do not see you can stop the guns themselves from working without radical changes affecting all normal life, but perhaps if you make use of guns very dangerous for the person using the the gun it could achieve the same result.

One avenue of thought might be something in the air which reacts violently with exhaust gases from shells created when bullet is fired. It might be chemical reaction, or it might be biological agents or nanobots which activates when those specific fumes are present (as most of normal life uses does not smell like gunshots, it would not create problems in normal person life, unlike most of the suggested answers)

Forgive me science if this is too absurd.

Disperse into the atmosphere molecules with 2 characteristics:

1. Their atomic nuclei are unstable enough to be smashed together (nuclear fusion) if they impact other molecules in the air at velocities that a bullet pushing the air can cause. Make the energy released enough to smash the bullet.
2. The new element produced by the nuclear transmutation is solid and strong enough to mostly contain the released energy (so that the energy release is localized and doesn't eg destroy the entire town).

Now when a bullet is fired the air pushes back and smashes the bullet then solidifies into a small ball which falls to the ground. You might even have it decay in some days or weeks back into the first element so the supply in the atmosphere stays more or less constant.

You probably have to invent a couple exotic chemical elements to make this work.

• And the first big volcanic eruption that happens will have really interesting effects... Not to mention the multiple tons of meteors that come screaming down every year... – Perkins Nov 21 '16 at 19:22
• This seems to break conservation of momentum. You initially have a forward moving bullet, a bit of nuclear fusion happens and suddenly the fusion products are falling downwards. – David Richerby Nov 29 '16 at 8:55

Yes, you can use millimeter waves to basically turn any matter into liquid, decompose the electron magnetism or extinguish flames if that's what you're after. It's a powerful wave and this device is theoretical ,but not particularly difficult to comprehend. It uses a series of magnetrons and a series of pulse guns oscillating at or greater than 192ghz targeted at the gun using a laser guide.

• What you are describing sounds like the Active Denial System, but at a different wavelength. I don't know about turning matter into liquid or putting out fires, but I've been hit by the ADS ('hey guys, go stand over there on that spot for just a minute....') and I'm still mostly solid, although it does make you itchy. Do you care to give more references to this equipment? – kingledion Nov 18 '16 at 20:58

Explosives are unusable if there is no oxygen, you are right on that one. However, guns can work even in a vacuum, as there is enough oxygen inside the bullet casing to allow for the chemical reaction inside them to take place. However, since it is a post-apocalyptic universe, newer bullets that are not made inside areas that have an atmospheric composition similar to that of the Earth will be unusable since there will be no oxygen to allow for their respective chemical reactions.

• While it's true that guns and bullets need oxygen (or any oxidizer really) to function, the ozidizer is rarely (if ever) atmospheric oxygen, usually something like a perchlorate or nitrate is used as an oxidizer (some hobby rockets use just sugar and potassium nitrate - to make it explode instead, just turn it into a fine loose powder and bingo), when it's heated it releases far more oxygen than the same volume of air, more oxygen means a bigger bang. – Samwise Nov 17 '16 at 21:15
• Ah thank you, I wasn't entirely aware. – Nora Nov 17 '16 at 21:16
• That's ok, it's not what I'd call common knowledge anyway – Samwise Nov 17 '16 at 21:26
• It's NOT common knowledge that gunpowder contains oxgyen bonded within chemicals, and the general public thinks it has something to do with atmospheric free oxygen!?!?!?!?!?!!?!?! I'm highly skeptical and mind blown... – ErikE Nov 18 '16 at 1:37
• Still, leave it around, I learned something reading it and the associated answers. (I'm always fascinated by how much there is to learn about very diverse subjects just reading worldbuilding's answers and comments) – spectras Nov 18 '16 at 7:25