Chinese Scientists 3D Print Gunpowder Substitute

    3D Print Gunpowder process (Yang et al, 2020)

    Chinese Scientists 3D Print Gunpowder Substitute - Graphical Abstract of the paper (Yang et al, 2020)

    3D printed firearms, emptying 3D printed magazines to fire 3D printed bullets against targets protected by 3D printed armor. It looks like the only element missing from the equation is to be able to 3D print gunpowder. Now, fittingly again thanks to China, we may see that too. However it may take a while, if ever, for this to become another tool in the toolbox of 3D printing gunsmiths across the world. Let’s see why.

    Chinese Scientists 3D Print Gunpowder Substitute

    Researchers from the Xi’an Modern Chemistry Research Institute published the paper titled “Fabrication and investigation of 3D-printed gun propellants” (Yang et al, 2020) on the July 2020 issue of Materials & Design. The peer reviewed document details the literature research on the study, the experiment setup and the results.

    Apparently, and maybe quite surprisingly, “additively manufactured gunpowder” is a thriving field of study, with several laboratories in different countries actively pursuing experiments. The research object (Yang et al, 2020) details the following as the potential advantages that these propellants may unlock:

    • waste minimization;
    • unconventional geometries not achievable with extrusion;
    • ease and convenience of manufacturing small batches;
    • reduction of time form manufacturing to gun firing;
    • weight reduction, miniaturization and integration of components.

    Most of these points are of major interest for large guns, rather than small arms, however some developments may have benefits across a wider range of ammunition. The study focuses on a 30 mm cannon round.

    The Experiment

    The researchers developed a special epoxy based resin, with a 50% composition of RDX high explosive in 25 μm size particles. Other additives were added to end up with a solution with 62.5% “energetic” content. The 3D printing process adopted is stereolithography (SLA), maybe it’s not as widely known as FDM/FFF but we’ve already seen it used for homemade firearm accessories. It works by accurately steering a UV laser across a thin layer of liquid resin which polymerizes under the beam, forming the solid part, layer by layer.

    3D Print Gunpowder - Diagram of stereolithography (SLA) process (Yang et al, 2020).

    Chinese Scientists 3D Print Gunpowder Substitute – Diagram of stereolithography (SLA) process (Yang et al, 2020).

    Before subjecting their explosive resin to the laser, Yang et al  performed several safety tests to avoid unwelcome outcomes. Once satisfied, they proceeded to print test specimens for several steps of material characterization. The pieces for the firing tests were manufactured in the the shape of Multi-Perforated Discs (MPD) and loaded in the shell of a 30 mm round, behind a 200g bullet (about 7.0 ounces).

    3D Print Gunpowder - 3D-printed MPD propellant stack (Yang et al, 2020).

    Chinese Scientists 3D Print Gunpowder Substitute – Photograph of 3D-printed MPD propellant stack (Yang et al, 2020).

    The muzzle velocity obtained was 420 m/s (1,378 fps), less than half of the conventional design, which can propel the same payload to over 1,000 m/s (3,280 fps). While the result may appear underwhelming, it is, however, a valid proof of concept. The researchers demonstrated the feasibility of a safe process to 3D print gun propellants. Their future focus will be gradually increasing the energy density and therefore pressure in the chamber, to make this solution as a viable alternative to conventional manufacturing.

    3D Print Gunpowder - Remaining propellant found in the gun chamber after test (Yang et al, 2020).

    Chinese Scientists 3D Print Gunpowder Substitute – Remaining propellant found in the gun chamber after test (Yang et al, 2020).

    For the readers fascinated by the concept, a similarly focused study, part of the literature research of Yang et al, is “Development of Propellant Compositions for Vat Photopolymerization Additive Manufacturing” (Straathof et al, 2019).

    3D Print Gunpowder Substitute - Propellant discs next to cartridge case (Straathof et al, 2019).

    Chinese Scientists 3D Print Gunpowder Substitute – Propellant discs next to cartridge case (Straathof et al, 2019). Note the similarities with the study in object. The case is from the 30 x 173 mm fired by the GAU-8/A.

    Will this translate in any advantage to the average shooter?

    In the medium term, most likely not. Main applications will be large guns, maybe offering advantages whenever the bullet/payload sits deep within the case, surrounded by the charge, such as in APFSDS or CTA cannon rounds. With reference to the latter technology, should Textron win the NGSW selection, maybe we could see some development in small arms.

    Surely an optimized resin recipe to 3D print gunpowder, available for reloaders aiming to achieve the highest consistency in burn rates, would be interesting. Sort of a smokeless version of what the Hodgdon Triple Seven Firestar offers to muzzleloaders, but with a wider range of load customization given by the 3d printing process.


    References:

    Weitao Yang, Rui Hu, Lin Zheng, Guanghu Yan, Wenrong Yan, Fabrication and investigation of 3D-printed gun propellants, Materials & Design,Volume 192, 2020, via: http://www.sciencedirect.com/science/article/pii/S0264127520302951

    M.H. Straathof, C.A. van Driel, J.N.J. van Lingen, et al. Development of propellant compositions for vat photopolymerization additive manufacturing[J] Propellants, Explosives, Pyrotechnics, 45 (1) 2019, via: https://onlinelibrary.wiley.com/doi/full/10.1002/prep.201900176
    Giorgio O

    Italian firearm enthusiast now living in an even more restrictive country, Giorgio has a passion for innovative or plainly unusual mechanical solutions. He’s also interested in manufacturing technologies with a recent focus on additive manufacturing.

    You can contact him at giorgio_o at zoho dot com and you’ll find him in the comments section as Giolli Joker.


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