# Would glass bullets be feasible in a hypothetical world?

Enter the world of hypothetical-ness:

Imagine a world where we have used almost all of our copper, lead, and iron supplies and deposits. The amount that we still do have is not enough to make a lot of bullets and military ammo.

But what if we could use glass as a projectile that could be shot from a gun or military weapon? What type of damage would it do, how would it change warfare, and how would cities change, and what would be the economic effect (i.e, now they are making glass in large amounts, how would that change the economy and areas with high amounts of sand, soda ash, and limestone)?

EDIT Also there is no way to recycle the metals: copper, lead, and iron.

The Questions

What damage could it do?

How would it change warfare?

How would cities change? (Defense)

What would be the economic change in areas with high amounts of sand, soda ash, and limestone?

• I'm assuming there's a reason they can't simply recycle the "used" metals? It's not like they disappear, so they could always be melted down and recycled -- unless something else is stopping that? – Kromey May 9 '15 at 0:16
• One less iron carcass flat and you have bullets for a good army. Cost of just one flat will provide you with a lot of bullets. If iron is so expensive, people most likely wouuld not use it for buildings but for smaller appliances. – Anixx May 9 '15 at 0:58
• Also, why not just use a different metal? Glass seems super illogical... – wposeyjr May 9 '15 at 2:51
• I'm sorry but the setting of this question makes zero sense. – o0'. May 9 '15 at 8:36
• @Kromey Maybe aliens just stole all our metals. – PyRulez May 28 '15 at 1:42

There are options available. Historically bullets have been carved from stone, for example.

The bigger problem to solve is what to shoot the bullet with.

A steel firearm quickly becomes priceless. You'd be killed for having one. I'd opt into archery in a world like this. Early bronze firearms exploded way too often for me to trust any firearm made of substandard material.

One less iron carcass flat and you have bullets for a good army. Cost of just one flat will provide you with a lot of bullets. If iron is so expensive, people most likely wouuld not use it for buildings but for smaller appliances.

That said, glass is by approximately 75% silicon dioxide ($\text{SiO}_2$). As such, if we have enough glass or sand we can extract silicon from it so ho have a metallic material much better suitable for making bullets:

• Do you have any basis for claiming that elemental silicon would be a better material than glass? It has a comparable density to typical glass. Elemental silicon is a metalloid, not a metal, and even if it were a metal, that doesn't mean it would have the properties of lead that make it effective for making projectiles. – smithkm May 9 '15 at 1:41
• @smithkm it is far more strong than glass. Glass bullet will not just survive the shoot. – Anixx May 9 '15 at 1:44
• I think the main impact of using glass for weaponry would be that the people doing it would get their asses kicked by anyone with a bit more sense. – Erik May 9 '15 at 10:13
• Yes. And since a bullet (either at firing or at target impact) is not subject to tension, I did wonder why you'd provided it. – WhatRoughBeast May 10 '15 at 4:55
• I don't understand "less iron carcass flat" – JDługosz May 30 '15 at 3:47

The problem is that for a good bullet, you want a very dense material that is also fairly soft. (Gold would be perfect, if it wasn't for the cost.) That's the main reason lead is traditionally used (until it became an environmental problem), and why depleted uranium is used for extreme military applications such as armor-piercing rounds.

Density is largely a matter of air resistance and penetration power, as the kinetic energy of the projectile is concentrated in less area. Softness is a matter of wear on the barrels of your firearms. Fire a few rounds of a hard, abrasive material like glass, and the rifling of your barrel will be worn down. A few more, and it could wear to the point where the bullets are a sloppy fit, compromising both range and accuracy.

• But you could use a dense hard substance if you coated it with a soft one. I always had a problem with Jose Farmer's Fabulous Riverboat and its use of plastic bullets. It makes more sense to use stone bullets and coat them in plastic. The same would work with glass bullets. – Jim2B May 9 '15 at 2:14
• @Jim2B I wonder if stone would survive being fired better than glass? – AndyD273 May 9 '15 at 12:59
• Not to be flip, but it probably depends upon which stone (material) you used. The Fabulous Riverboat guns used slower burning black powder instead of cordite or gun cotton. – Jim2B May 9 '15 at 16:51
• @Jim2B: Sure, you could coat the bullets, but that gives you a more complex manufacturing process, and thus makes each round more expensive. At what point does it become to expensive to shoot your guns? Note another problem, too. With current designs, the (usually) brass cartridge contains the powder, and forms a gas-tight seal in the breech mechanism. You'd have to redesign the whole mechanism, especially if you want semi-automatic or automatic weapons. – jamesqf May 10 '15 at 5:08
• "Fairly soft" is not exactly what you want for armor-piercing rounds. See tungsten which would be used to that end instead of uranium. The latter being mainly used for cost reasons if one has incidentally access to large piles of depleted uranium (say because one maintains a nuclear weapons or energy program). – Ghanima Jun 1 '15 at 19:24

Glass has a density of $\mathrm {2.4\ g/cm^3}$. This is going to be a serious limiting factor in how much damage the bullet does when it hits—it will not penetrate more than 2.4× its length. That means a small-calibre bullet isn't going to do a lot unless it hits something vital that's near the surface (say, an artery—and even that only means you likely get a kamikaze enemy. They know they're going to bleed out and try to take you with them.)

• Making long needle-like bullets (probably saboted) would help, as long as they didn't just shatter on impact. I suspect it would be easy to armor against glass bullets. – user243 May 29 '15 at 16:30
• Indeed, given the problem of making gun barrels out of anything but metal, I would wonder why the society would bother with guns. Crossbows work quite well with wooden quarrels. Evolving technology might take a path that leads to some sort of explosive-propelled derivative of that. – jamesqf May 30 '15 at 18:46
• I'm interested in knowing why the density relates to penetration depth. I mean, I realize that physics would say that it is, I'm just curious about the math involved to go from X-g/cm3 to X*length. – Draco18s no longer trusts SE Jun 21 '17 at 17:27
• @Draco18s It's relative density--a high speed projectile will be basically stopped after displacing it's own mass. The body's density is close to 1 g/cm^3 so it looks like penetration depth = density but that's not true in all cases. – Loren Pechtel Jun 21 '17 at 21:40

I recall a short story about a planet without accessible metals. The beings there were adept at making ceramics for all purposes.

A planet like that presumably still has Aluminum, which is very light and doesn't exist naturally in metalic form. Other metals that are never present as metal (requires high level of technology to isolate), and low on the periodic table might still be present.

Look at this link for a list of non-metalic metals by density. The densest at 11.2 is mercury oxide. The next one (9.8) contains bismuth and chromium. You would have to go down the list to find what is allowed, but it will be lighter. Lead, in comparison, is 11.3 and iron is 7.9.

Higher tech would not be to use glass. They would find a mineral (possibly synthetic) that has desirable properties such as (relatively) high density, or being monocrystaline and able to withstand high stress.

Projectiles made of flint were effective, long before firearms came around. Perhaps combustion as a way to throw an arrow would be a natural progression from hand-cocked springs of various types. Hard needle tips might evolve, as opposed to heavy slugs. They could certainly be poisoned as well. Morter rounds can contain flaming tar and diseased rat carcasses as well as stone. Explosive rounds might deliver the punch after the projectile reaches its destination.

Since glass is far less dense than metal, the only way to increase the penetrative and killing power of a glass bullet would be to make it go far faster than a comparable calibre metal round. The magic equation here is $E_k=\frac12MV^2$

Of course the difficulty them becomes:

a. How do you drive the bullet so fast, and;

b. How will the projectile stay together?

Since glass is rather brittle, a glass bullet will shatter if subjected to high accelerations. Since glass is actually an insulator, electrical weapons like railguns won't work with a glass projectile (unless saboted in a metal case), but then you will end up blowing a slug of molten glass or glass dust out the barrel at about Mach 7.

So glass is probably not the thing you are looking for here. Maybe if you use basalt spun into a bullet form, you will be closer to a usable weapon.

Purely hypothetical but say hardened glass, almost like gorilla glass or unbreakable pipes for smoking, I have seen those thrown on the ground and not break, were used and hypothetically we could fire it without breaking... Wouldn't the actual wound be a lot worse than metal due to it shattering as it penetrates flesh then fragments and slices? Or because of the mass it would create more of a flesh wound?

Glass could perhaps be used for a small caliber bullet in space or on the moon, as the propelling force would be less than on Earth. It would be cheaper and more economic than mining, transporting, and then probably just wasting the more valuable stuff.

• Welcome to WorldBuilding hil! If you have a moment please take the tour and visit the help center to learn more about the site. Have fun! – Sec SE - clear Monica's name Jun 21 '17 at 14:11
• why would propelling force be lower on the Moon or in space? You mean the lack of atmosphere? I don't believe it is issue huge enough to make a difference. – Mołot Jun 21 '17 at 14:25

To supplement the answers above, people do make glass bullets (more accurately, shotgun slug). While the glass shatters on contact with hard surface, it can still penetrate a thin metal sheet, and the fine glass powders continues to move in forward direction.

Which also suggests that hitting body tissue will do much more than a superficial wound, more likley a penetration wound heavily contaminated with fine glass powder.

A youtube video with glass bullets, 1:20 onwards

As a side-note, lower density not only reduce penetration, but also causes the projectile to decelerate more rapidly in atmosphere, reducing the effective range of the weapon used.