Ammo for 3-D printed guns

The plastic guns being made have been tested with conventional ammo intended to be fired in conventional guns. Why not load up some low pressure rounds specifically intended to work with the plastic guns?

Even if the bullets had muzzle velocities half that of conventional guns you aren’t going to get volunteers to be bullet backstops. Choose a common cartridge which already has a fairly low pressure then tweak the bullet weight and powder charge to get something that the plastic is much more capable of handling.

Here is a list of max pressure recommendations in PSI for various cartridges with the obvious high pressure cartridges removed:

380 Auto 21,500
25 Auto 25,000
32 S&W Long 15,000
38 Auto 26,500
38 S&W 14,500
38 Special 17,000
44 S&W Spl 15,500
45 Auto 21,000
45 Colt 14,000


36 thoughts on “Ammo for 3-D printed guns

  1. Of course, at the ranges a plastic gun could be fired accurately, low pressure rounds would still be quite deadly.

    Add in the developed of the new Poly cased rounds, and pretty soon you’ll have a gun that could easily walk right through a metal detector.

  2. Of that list, I’d think the .45 colt would be the best choice. Rimmed, already low pressure and designed to toss large hunks of lead. Seat a 250 gr soft lead HP deep, a light charge of powder (something like maybe 5 gr of TrailBoss), and you’d have a pretty modest load, but still not something I’d like to meet from the wrong end.

  3. Hmm. There is some history of highly effective, low pressure loads. Several hundred years of it. It may be that the pressure curve for a black powder charge results in higher velocity from the same peak pressure. That’s what some people say anyway. I have no data. I’m something of a black powder freak of late, so it came to mind right away. It’s very dirty compared to smokeless of course, but it may have some advantages where your working pressure must be very low.

    • I know when smokeless powder was developed most old guns that were designed for black powder weren’t able to handle the new powder’s pressure, so you may have something there, and the advantage of plastic not being able to rust you eliminate the main drawbacks of black powder, namely having to be cleaned as immediately after firing as possible to avoid rusting!

      Black powder is a mix of charcoal, sulphur and saltpeter, which I believe burns slower than the the nitro based smokeless powders. So I’d assume it has less of a pressure spike than modern powders.

  4. I’d love to load up a 10mm plastic bullet with a double charge. something tells me up close and personal;…. You’re gonna have a bad time.

  5. Non-metallic primer? Don’t know of any. BTW, if you have worked a metal detector station or taken the training video series, you will know that most plastic items can be identified as to shape/outline.

    Got to think outside the “gun” box, people. The components have to exactly resemble the detector video signature of permitted and innocuous items. What you will wind up with is some sort of a boosted blowgun + darts. The tube will be a walking cane. Go from there.

      • Scaramanga!
        Scaramouche is the literary hero from the book of the same name by Rafael Sabatini (Great-great uncle of a childhood friend, btw), who “was born with a gift of laughter and the sense that the world was mad” (a useful gift, btw).

    • The active ingredient in primer is not metallic — it’s a compound (like mercury fulminate or lead azide or whatever people like these days). Standard primer assemblies use a metal cup to hold the active ingredient, but that’s not essential. Similarly, the propellant is non-metallic. Non-metallic cases can be made, as can caseless ammo. That leaves the projectile. Some ceramics (zirconia) have density around 6, which is not much less than steel. And tungsten carbide has a density around 15 — wrap a little plastic around that to engave the lands (if you have lands). So it sounds like all the metal can be eliminated.

      • Eliminate the whole cartridge-like paradigm. Go to a stacked system with multiple rounds in a single, discardable barrel (a prototype of that was shown a few years back, with some incredibly high rate of fire). Electronic ignition. Disposable barrel section clips to a mating dovetail on the top of a smartphone case, using the smartphone electronics for the fire control group, communicating by bluetooth. Looks like a Sharpie marker and a cell phone when disassembled.

      • Those plastic children’s caps are basically primers on a plastic cup. Basically a plastic berdan primer ready to use.

  6. Plastic printed guns will be obsolete soon anyway. The patents on selective laser sintering expire in the near future, meaning you’ll likely have a way to print metallic parts at home before long…

  7. Also I wonder if you could both A) allow for printed rifling on the barrel and B) get better velocity from the lower pressure, if a polymer driving band was added to the bullet, and either use an over-sized barrel, or an under-sized bullet and let the driving bands allow for accuracy and lower barrel friction, so higher velocity.

      • Ok, well we could get into a hair-splitting argument about the differences between a driving band and a sabot.

        Of course after I hit “post” I realized a sabot or a paper-patch would probably be much easier to make.

        But you get my point.

        • Oh, there is NO hair-splitting argument between a driving band and a sabot — but it is pretty pedantic. 😉

          Hell, at the ranges something like this would be used, round ball and smoothbore would be fine. For a higher pressure version with improved materials technology, go with a fin stabilized or Diablo profile.

  8. A good place to start might be the Speer practice cartridges; a 38 Special plastic case & plastic bullet powered by a large pistol primer.

  9. In the book “Unintended Consequences” the protagonist used a nylon bullet at very high velocity to defeat body armor. Short range only, but supposedly the light projectile goes fast enough, long enough, to penetrate at least some types of kevlar vests.

    The recipe as I recall was a case full of bullseye in a 44 mag, with a projectile turned from a nylon rod – no specific weights were given.

    I wonder how much pressure a normal load would have with a similar lightweight projectile?

    • a case full of bullseye in a 44 mag

      This is in a novel, right? I wonder, in the real world, how a nylon projectile survives being launched by that load?

    • Actually, that bullet wasn’t used to defeat body armor in the novel. It was used as a short range self-defense/execution round, and the only time in the novel it was used was to kill the ATF director on an airplane in a way that wouldn’t damage the aircraft.

      As for the type of round you would use, put me in the “black powder/BP substitute” camp.

      Actually, if you make your plastic gun a muzzleloader, or something like a muzzleloading pepperbox if you want multiple shots, it’s exempt from the newly reenacted undetectable firearms act, as muzzleloading guns aren’t legally “firearms”.

  10. The standard anti-tank round for the M1A1 tank is a tungsten sabot dart, driven at 5,000 fps. It “burns” (spalls) the target tank’s armor plate with pure kinetic energy, then sprays the interior of the target with superhot molten steel from that penetration, killing the crew and detonating it’s ammo supply.

    Woven body armor could be similarly defeated by a high speed dart that slips through the weave. The minor wound caused might not be a stopper, though.

    • Can be dealt with by proper balancing of CG and/or frangibility.

      Darts that go through armor can be easily made to destabilize quickly — it’s just bloody expensive to do it for small arms ammo that will be consumed in quantity.

  11. How about a 12-gauge shotgun shell? Normal pressure 11,500 PSI. Download it to half that, and shoot a 438 grain slug at maybe 600 fps. There are already a bunch of goofy projectiles made for it, and sabot rounds. Don’t have to invent anything new.

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  13. From what I know about 3d printers and a little about material sciences the bigger the bore you have to make the more layers of plastic there are going to be bisecting the bore and creates more weak points as well as having to drastically increase the chamber wall thickness, so untill the material gets stronger large caliber and bottleneck cartridges are impractical. Why hasen’t someone just made one in .22 short?

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