Should we be afraid of them?
…should we be afraid to live in a world where anyone can afford the equipment to manufacture a gun in his or her basement? I hope not—because that’s the world we live in now. Guns are comparatively simple devices. In fact, plenty of custom firearms are manufactured today using equipment that wouldn’t be out of place in a basement. Just as the sets of “plastic guns” and “3D-printed guns” are not identical, the sets of “3D-printed guns” and “homemade guns” are not identical. At the moment, virtually every homemade gun is constructed using some technology other than 3D printing.
Yes, as with most hoplophobia, this is silly.
Machinists are laughing.
Yes, I am indeed afraid of printed guns. How do I know one of things won’t blow up in my face when I shoot it?
Not all 3D printers are the same. Some admittedly quite expensive ones can make metal parts such as the one used to produce this metal M1911 .45 pistol. They’ve fired over 2000 rounds through it so far without a malfunction. They’re offering to sell them as collector’s items for the low, low price of $11,900. I think I’ll wait for the price to come down.
I always thought a nifty way to try and make a rifle barrel was to take a spent (and thus rifled) projectile, dip it in some ferric chloride circuit-board etchant to thin it down by a few thousandths, and then use it as the tool for electrochemically machining the barrel with a high-current, low voltage power supply (about 5 volts) in a high-flow salt water solution driven by a pond pump. A simple op-amp circuit could index a piece of all-thread to maintain constant current through the tool (which is negative, while the barrel is positive). Then you’d take a cartridge and use it as the tool for etching the chamber. That should let ordinary folks make a rifle barrel out of just about any piece of steel, even cam shafts from a junkyard. But I never actually tried it.
Instead I spent my time drawing up a way to make a rather conventional looking semi-automatic pistol that extracted the cartridges rearward, to allow a significantly longer barrel in the same frame. It took me years to come up with a simple way to do it (simpler than a Browning), but unfortunately the shooter would have to cycle the slide manually when reloading a magazine, because the slide has to be forward to grab a cartridge, and then has to pull it back to extract it from the magazine, and then release forward again to chamber it. That would be irritating. Or you have to add a complicated spring arrangement to store the energy from the last shot from the previous magazine, and release it when the new magazine is inserted. That adds complexity.
So then I thought of making a pistol where the barrel and magazine float relative to the grip, with a narrow-field camera that looks backwards to find the center of the shooter’s eye (a nice bullseye target for a computer to center on), and then use two servos to keep the barrel locked in a direct line to the eye, turning the pistol into a more stable platform than a rifle and allowing close to MOA accuracy (in a suitable gun) with only a sight post or target dot. The shooter wouldn’t have to align two sights, and the wrist would be out of the aim equation. As an added bonus, the pistol could be locked to a particular person’s iris, and could even be programmed not to fire without the lock so a person couldn’t even shoot themselves with it, except perhaps in the foot. If you got really crazy, you could have the gun take a nice picture of the shooter’s face (via the rearward facing sight camera) and transmit it into a tiny little memory chip in the bullet an instant before the bullet is fired, so forensics wouldn’t even have to do anything to solve the crime. But such a gun can’t be sold because the first time somebody shot the wrong person, they’d blame the gun’s targeting mechanism for the failure and the lawsuits would fly thick and fast.
So my last gun idea was to try and switch a rifle to a hybrid propellant to get much higher muzzle velocities. At first I was going to use plastic shavings or chips, loaded just like conventional powder, with nitrous oxide in the cartridge to act as the oxidizer (just like a common hybrid rocket engine) but there might be a small leakage problem around the primer or case neck. So I thought it might be better to take a spool of very small diameter plastic tubing, pump the oxidizer through the entire tube, and then seal both ends. Then run the tube through a pair of warm spur gears, meshed so their teeth almost touch instead of mesh, to weld the long spool of tubing into small, discrete “bottles” an eighth to a quarter inch long, then have the spur gears followed immediately by a cutter. That should turn out individually sealed plastic pellets, each filled with a pressurized oxidizer, which could be used without even modifying standard reloading equipment.
But the one thing I never thought of was using a 3-D printer to build a revolutionary type of weapon, because how you make the parts is a separate question from how the parts have to work.
Congratulations, George. In your first paragraph you have re-invented electro-destructive machining (EDM).
I haven’t heard of that, though I did take apart an old EDM machine last week (mid-1980’s vintage, with tape drives!).
I leaned toward ECM because it doesn’t have tool wear (so the barrel will be a consistent diameter) and will leave a smoother surface finish. With precision ECM you can get a surface finish better than 0.05 microns, with the downside of taking 18 hours or more to drill a 22-inch barrel. But mainly I liked the idea of using a fired (and thus already rifled) bullet as the tool.
Maybe everyone here knows this story, but the whole Industrial Revolution was based on heat engines (steam engines), and Thermodynamics, the science of heat engines, came from . . . boring out gun barrels.
Drilling the bores of cannon, actually. There was some dude who was grabbing the metal shavings from the machining and plunging them into water to measure the heat generated, and this was the key to understanding the equivalance between heat energy and mechanical work. This helped disprove the Phligoston theory, putting Chemical Thermodynamics on its modern footing. I bet the tech to machine gun barrels also was helpful in making cylinders for steam engines too.
That’s very interesting! One of the disadvantages of ECM is that it’s very inefficient compared to conventional machining, measured as Joules or HP/hrs required to remove a given volume of steel. That of course spurs lots of research, and things like using lasers to better direct the dissolution.
One of my hopes was that since the tool isn’t under a large compression load, the drift that occurs in conventional gun drilling could be avoided, eliminating the need to put the barrel in a barrel straightener, which can leave residual stresses that cause the barrel to walk as it’s heated during repeated firing. A sniper rifle I used to have had its barrel cryoquenched to help prevent this, converting any remaining austenite to martensite. And of course a gun drill and barrel straightener aren’t remotely cheap, and on top of that you need a button rifling rig, and a chamber cutter, etc. A spent bullet, a piece of copper all-thread, a used cartridge, some surplus PC power supplies, some salt, and a big water pump sounds so much cheaper – if it works.
Anybody remember “The Weapon Shops of Isher”? We could use a couple (thousand) of them.