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I had an idea for a world where tin and copper are both easily accesible and usually found close to each other enough that it is a non-factor. Bronze is pretty much the main alloy for use in anything, since iron is very rare. It exists and people are even pretty competent at handling it and making good quality steel, but it is rare enough that only a select few people can reliably make use out of it. Hence why steel is ony used for things bronze can't reliably or realisticaly substitute for.

My question is this; what would small arms look like in this setting? Bronze is awesome, but it is not steel. It has different properties. So I am wondering what exactly bronze firearms could handle and what sort of limitations I would have to keep in mind.

I know artillery was made from bronze in the past, Austria Hungary used something called 'Steel bronze' in WW1. https://en.wikipedia.org/wiki/8_cm_FK_M._5

That said could you make a handgun, rifle, submachine gun or a machine gun out of bronze? And if yes, what are the limitations? I found somewhere that rifling probably wouldn't work too well due to bronze being softer, but maybe there are ways to bypass that specific issue.

Things to keep into account;

-This is more along the lines of a hellish dimension than a natural world. So sometimes things are the way they are, because higher powers decide they are. I am willing to handwave provided it is within reason.

-The people are in a near constant state of war due to the machinations of these higher beings. Trade happens, but cannot be relied upon.

-People aren't born into this world, they appear with amnesia. They do keep echoes of their memories. This makes it so that concepts such as heavier than air flight are known, but it's simply a matter of "How does it work exactly?"

-The tech level that I envision is around WW1 era, though if certain factions could plausibly make it I am willing to handwave it. (So no needing nuclear power or needing microchips or something like that.)

-Factions range from small clan sized (a couple dozen) to larger 'empires' whoms total manpower (not just soldiers, but craftsmen, farmers, etc as well) can go into the 10-15K range. Anything more is hard to keep together for 'longer' periods of time.

-Feel free to use bronze alloys such as manganese bronze if it helps.

-Iron and steel parts should be kept to an absolute minimum, maybe a bit can be excused, but weapons are competing with other important things for the limited amount of iron/steel available to most factions.

-If propellants such as smokeless powder or blackpowder are entirely impossible, would pneumatic rifles work?

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    $\begingroup$ "Bronze" is a very, very broad term. Any alloy of copper other than with zinc (which makes brass) is a bronze. Bronzes range in strength from barely harder than pure copper to significantly stronger than mild steel. Most of those, however require more alloying agents than just tin to be added to the copper. $\endgroup$
    – Zeiss Ikon
    Nov 25, 2020 at 13:14
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    $\begingroup$ @ZeissIkon Such alloys are allowed to be used in an answer. "-Feel free to use bronze alloys such as manganese bronze if it helps." $\endgroup$ Nov 25, 2020 at 13:18
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    $\begingroup$ Bronze barrel black-powder small arms historically were commonplace so plausibility is fine with black-powder pistol, rifle, shotguns, and even grenade launchers (see here for examples ambroseantiques.com/flongarms.htm or search for "bronze flintlock"). My guess is that where you would run into trouble is with both more powerful smokeless propellant and fully automatic weapons where bronze's lower strength and wear characteristics become problematic. A bronze gatling gun might be plausible but SMGs, ARs, and machine guns might not be. $\endgroup$ Nov 25, 2020 at 16:01
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    $\begingroup$ It might be possible to ameliorate some of the limitations by using steel barrel liners in bronze barrels to reduce steel usage or more frequently swapping out barrels. This could make modern heavy machine guns plausible. However this affects both troop maneuverability, logistics, and expenses because more and heavier bronze replacement gun barrels need to be purchased and carried around. $\endgroup$ Nov 25, 2020 at 16:36
  • $\begingroup$ tin and copper are both fairly rare and almost never occur close to each other, the long distance trade needed to get both was part of the reason bronze age civilizations were so interconnected and contentions. $\endgroup$
    – John
    Nov 26, 2020 at 1:06

3 Answers 3

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There's a broadness to this question that sort of encompasses a lot of various engineering issues. While it's true that general bronze (and here I'll mean specifically the tin/copper version) does not match up to steel, there are still measurable values for what that bronze CAN do.

As such the firearms would be built with those limitations in mind. To keep things simple, lets just say bronze can only handle half the pressure/force of steel (and this is a simplification that ignores more rigorous details like compressive strength, hardness, etc.)

But simple example lets us get a couple of clear solutions:

  • Use twice as much Bronze, double the thickness of your barrel and components (More weight, same performance)
  • Reduce the powder charge of you bullets to half of what you would use for steel (Similar weight, less range and/or muzzle velocity)

We're roughly just concerned with the end results concerning forces here. It's also worth noting that the alloy itself is only a part of the end product. Reading the wikipedia article you linked on "Steel Bronze" suggests that it's basically a mechanically hardened form of (i'm guessing tin/copper, since they don't specify there) bronze.

So even if you do have to hand-wave something, you can make it sound like a scientific or industrial process with only minor explanation. "The benefit of the McGuffin process was pronounced, Bob had never held a fire arm this light weight; or this powerful in his life."

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    $\begingroup$ You need to be careful concerning the availability and cost of steel. Suppose it was "only" ten times more expensive than bronze, then bronze guns with one tenth the amount of steel carefully used to maximise barrel strength might be a thing. Also think about other metals that might find a use in the absence of steel Manganese? Nickel etc $\endgroup$
    – Slarty
    Nov 25, 2020 at 17:02
  • $\begingroup$ Though the barrel would need to be thicker, the components don't necessarily need to be of double thickness. There's a prototype M1911 pistol whose frame is made of an bronze alloy named Brastil that is shaped the same as a regular steel M1911: thefirearmblog.com/blog/2009/09/10/the-bronze-1911-pistol $\endgroup$ Nov 25, 2020 at 21:17
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    $\begingroup$ @GrumpyYoungMan note the major reason brastil alloy was considered a failure was it warped through use, rendering the gun inoperable after only mild use. So you do need a much heavier weapon. $\endgroup$
    – John
    Nov 26, 2020 at 1:22
  • $\begingroup$ Hmm...there will be a lot of different firearms based on a factions capabilities; from high grade bronze rfifles that will probably be forced to use blackpowder or use pneumatic power to those with some steel and the high end full steel ones using smokeless powder. That said could a firing pin be made out of bronze for example? I do intend all firearms to at least use casings. Does there exist a bronze alloy that can serve as firing pin or is this one of those components that need to be steel? $\endgroup$ Nov 26, 2020 at 15:38
  • $\begingroup$ @TheShadowOfZama - Search on "bronze firing pin" and you'll see mention of some American firearms from the end of the 1800s that used bronze alloy firing pins. "Aluminum bronze" and "phosphor bronze" is mentioned as materials $\endgroup$ Nov 26, 2020 at 21:22
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Barrel pressures will be lower.

High velocity rounds require high barrel pressures and the tensile strength of bronze may not be up to that in the way steel is.

But there is a workaround. Consider mv2 which describes the kinetic energy of a projectile. As it increases with the square of v you get more bang for your buck (so to speak) by increasing v.

In your world, they increase m. Cannons made of bronze are fine, because barrel pressures are low. And the destructive power is high because cannonballs are massive. In your world, projectiles are as heavy as they can be. Also, a long barrel allows more time for a low pressure charge to accelerate the projectile.

You can replicate to some degree the stability conferred by rifling through changes in projectile design. I am a fan of the Taofledermaus youtube channel and one of the coolest ones was this self-stabilizing dumbell shotgun round.

https://www.youtube.com/watch?v=M7f4tEMrg4I dumbell round

So for your world of bronze, in the interest of maximal awesomeness.

1: Long guns!
2: Massive projectiles.

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    $\begingroup$ Good summary. Given the question is focused on small arms, may be worth summarising in the last 2 lines that long guns = heavier guns and massive projectiles = heavier ammunition. Infantry will either be carrying less ammunition or much heavier loads or both. Also worth looking at the much lower melting point of bronze vs iron and how this will limit the number of rounds fired by automatic weapons in a given time period. $\endgroup$ Nov 26, 2020 at 3:21
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    $\begingroup$ making the projectile heavier also increases the pressure inside the chamber, so it poses the same problems as increasing the load. Bronze cannons worked for the same reason bronze small arms worked, they were overbuild (and thus very heavy) to withstand the forces. $\endgroup$
    – John
    Nov 26, 2020 at 5:42
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    $\begingroup$ This is very interesting, using the bullets to essentially do the job of the rifling. Reminds me a bit of the Whitworth Rifle. en.wikipedia.org/wiki/Whitworth_rifle Since rifling would be a problem with bronze barrels would it be logical to see developments along these lines as well? $\endgroup$ Nov 26, 2020 at 15:29
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They will wear out faster and either be weaker or heavier (or both)

this can very easily be compared by looking at cannons and guns made of the materials. Bronze and iron cannons as well as smaller guns were produced at the same times.

Bronze is weaker, heavier, more costly (rarer materials), and softer(wears out faster), but it does work.

The big disadvantage iron had was consistency it was much harder to make iron of the right quality, and more importantly harder to tell you had made the wrong quality so early iron cannon could fail without warning. Iron is technically harder to work with but in all there regards it is a better material. but by WW1 most industrial coutries had solved this problem (although not ALL of them, a handful of nations like Austria-Hungary could not manage it for large artillery's pieces)

So you can make a bronze gun, but it will be heavier, weaker (in terms of power), more expensive, harder to get material for and, wear out faster than an iron/steel equivalent. You can make a rifled bronze barrel it just wears out quickly. A bronze machine gun will suffer extreme barrel wear, keep in mind early machine guns wore out STEEL barrels at an alarming rate bronze will probably have to be swapped after each use.

Weight and weakness can be traded for each other up to a point, (make a thicker heavier barrel to increase power or decrease power to lighten the weapon) but you can't really change the other two factors, and you still end up with more weight becasue of things like bronze springs, ejectors, and firing pins. Weight may make some of them unwieldable.

At WW1 tech levels Bronze offers no advantages, but firearms made using it can be made if you are determined enough. Also keep in mind WW1 technology requires industrialization. They will also need steel for the tools that make the firearms.

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  • $\begingroup$ Bronze actually started out cheaper than iron. The OP posits a world where the Bronze Age Collapse never happened; hence, there was no period where bronze was practically impossible to make, so there was never a reason to invest heavily in iron smelting and the appropriate tools. The rest of your answer has merit; the wartime need for stronger metals could still drive a compelling need to invest in the necessary tools and furnaces to make steel. $\endgroup$ Aug 16, 2023 at 14:52
  • $\begingroup$ @CodeswithHammer bronze started cheap up until people learned how to smelt iron, bronze has huge unavoidable transport costs because you need two rare materials that do not occur in the same place. there are billions of iron source in almost every type of terrain. $\endgroup$
    – John
    Aug 16, 2023 at 15:04
  • $\begingroup$ IIRC iron didn't replace bronze until after the Collapse. You're absolutely right that bronze has a higher transport cost than iron; but the transition still requires a need for a civ to invest in iron smelting. Like all major tech developments, iron had a higher capital investment and a lower use cost than bronze. $\endgroup$ Aug 16, 2023 at 15:15
  • $\begingroup$ No iron has a far lower capital cost, the cost of smelting iron is marginally larger the cost of raw material is drastically lower or iron. the benefit is simple economics, i can outfit 100 soldiers with iron weapons for the cost of outfitting 10 with bronze weapons and an outside force cannot easily disrupt my source. Iron prior to smelting was made from meteorites or native iron which is very rare, but once smelting and basic forging is invented the advantages of iron is overwhelming. the need being filled for for metal weapons and tools. $\endgroup$
    – John
    Aug 16, 2023 at 15:28

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