Does anybody know if there's any formula for (relatively) smokeless firearm propellants that can be produced without the amenities of modern industry, especially without the widespread availability of pure chemicals? I'm thinking of a post-apocalyptic scenario here, where modern industry and international trade is basically gone, but a fair amount of our modern know-how is still preserved (if rather haphazardly). The propellant formula and its production process must have been developed before the crash, of course -- perhaps for the exact eventuality of such an industrial breakdown.

If there's no such thing, I suppose I can always fall back on black powder . . . .

(P.S. : if any of you is wondering, yes, it's for fiction. I'm not keen on going into that kind of extreme survivalist mode just yet.)

As far as my basic understanding of chemistry is concerned smoke is largely made up of parts of the original mixture carried away with the expanding gasses that make up the explosion which haven't reacted for some reason.

Thus minimizing the amount of smoke would need a near perfect reaction which needs a) very pure chemicals as any impurities will interfere with the reaction, b) very precise mixtures so the stoichiometric ratios are as perfect as they can be and c) very evenly mixed reactants.

While technically possible by hand - provided you have enough time, resources and high-tech equipment such as very fine balances for example - I doubt that this can be achieved for any practical purposes or at any efficient rate to be actually usable.

The funny thing, black powder made with just charcoal and saltpeter IS smokeless; it just has a higher ignition temperature that sulfur containing powders and a slightly lower amount of energy when compared to the "perfect" powder mix. a normal primer in a cartrige loaded with won't have a problem firing, but flintlocks and wheelocks did not handle it as well, due to the higher ignition temperature. matchlocks however can shoot it fine. Not technically needing sulphur to produce powder takes away one of the main stumbling blocks to firearm production- sulfur supply, which in the pre modern era needed to be mined,not synthesized.

and despite some misinformation out there on the internet, modern cartirges loaded with black powder shoot fine, just with the kind of smoke cloud you'd expect from blackpowder

http://www.musketeer.ch/blackpowder/recipe.html

How about guncotton? Basically nitrated cotton,also your forgetting the primers which are an important part of getting a safe reliable ignition with the smokeless type powders.So maybe you need to look at the old mercuric type primer mixtures.Chlorate based powders are also an option.

Every formula for smokeless powder that I have ever heard of requires nitric acid. Nasty stuff and hard to obtain now. Some also require sulfuric acid which is easy to obtain and not nearly as nasty.

On the gripping hand, Black powder can be made from charcoal, sulfur and chicken manure. A much more likely product after TSHTF.

Given the original question , nitric acid is surprisingly easy to make , even with improvised methods.And its used in a large number of commercial and industrial uses so scavenging is a possibility.It can be made with potassium or sodium nitrate, and nitrate based propellants don't require a source of sulphur, which you'd need to either mine, or extract from scavenged materials.