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Long ammo

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(+4)
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3D-printed guns have been designed, made and tested.

One of the biggest problems in creating a _fully_ printed gun, using common plastic printers, is the barrel/chamber. This part of the gun is subject to enormous loads, meaning that even a bulky printed gun has a limited lifetime and/or can only handle small ammunition.

However, there might be a solution to this. There is no reason why the casing of the ammunition could not be substantially extended, so that the casing itself acts as a short barrel. It might even be possible to include some basic rifling.

You would not get the combination of accuracy and affordability of a conventional, precision-engineered gun barrel and normal ammo, but such "long ammo" would act as a reasonably cheap disposable barrel for a 3D printed gun.

MaxwellBuchanan, Oct 30 2015

Gyrojet https://www.youtube...watch?v=qpOcdyxvUvc
As mentioned in an annotation. [Vernon, Oct 30 2015]

Bronze fill https://www.youtube...watch?v=nDoYO22103Q
Bronze and plastic for platic extruders. [travbm, Oct 30 2015]

[link]






       You might not need rifling — simply streamline and weight the tip and put flights on the trailing end.
Ian Tindale, Oct 30 2015
  

       There is a type of gun called a "Gyrojet", in which each piece of ammo is a small rocket, and there are no significant pressure stresses on the barrel (but lots of temperature stress). See link.   

       Perhaps you could go to a ceramics workshop to make Gyrojet barrels, and then 3D-print in plastic the rest of the gun?
Vernon, Oct 30 2015
  

       They have made 3d printed metal composites such as bronze fill and carbon fill even wood filled polymers. So you could make a nice little rifle to even your own shot gun shells.
travbm, Oct 30 2015
  

       [travbm], the 3D printing machines that handle metal are far more expensive than the ones that handle plastics. Your average home-owner isn't going to have one of those for quite some time (price must come down).
Vernon, Oct 30 2015
  

       I know you can 3D print in metal. For that matter, you can make a perfectly serviceable barrel by machining it from the appropriate alloy. There are even companies that do this routinely, and sell complete guns which seem to work well. There's a little outfit called James Purdey & Son in the UK, for instance.   

       But the idea was to develop ammunition which, by using the extended casing as a single-use barrel, would simplify the production of plastic firearms. In effect, the round becomes, almost, a disposable gun, requiring the addition only of a handgrip and trigger.
MaxwellBuchanan, Oct 30 2015
  

       Don't need 3d printing, or long ammo. You can make a magazine loaded zip-gun to fire any round if you're not worried about accuracy. Long rounds with rifling would just make it easier.   

       [travbm] doesn't mean a metal 3D printer. He means using a regular plastic 3D printer like many hobbyists have with a plastic filament that has metal particles in it. Such filament already exists. However, I don't know if that would be good enough; the heat would still melt the plastic holding the metal particles together, I'd think.
notexactly, Nov 08 2015
  

       Custom cases will attract the ire of the Alcohol Tobacco and Firearms people, I think. (I wonder if these items are similarly grouped under one body in other countries).   

       Why not just have the barrel be as long as a standard casing? You could have it be a pistol that fires rifle bullets. Those have big casings.
bungston, Nov 10 2015
  

       Some part of the weapon has to act as the chamber which is subjected to 35,000 or so psi from a hot pistol round and maybe 50,000 psi from a rifle round. (+) for innovation.
cudgel, Nov 10 2015
  

       Can't the casing be the chamber?
bungston, Nov 11 2015
  

       If the ammo was, say, 2 metres long and the person your were trying to shoot was also 2 metres away, then this becomes a long stick to poke people with.
hippo, Nov 11 2015
  

       Plus even if they did not like getting poked they would not lip off, because a bullet could come flying out of that long stick.
bungston, Nov 11 2015
  

       //Some part of the weapon has to act as the chamber//   

       So, a question. How much of the pressure is taken by the casing, and how much by the chamber that contains the casing? If you were to fire a regular rifle bullet with nothing around it, would the casing burst?
MaxwellBuchanan, Nov 11 2015
  

       Yeah, what he said.   

       I worry that the gun aficionados have become irregular visitors to the HB.
bungston, Nov 11 2015
  

       Are you worried that they're not regular, or that they're visitors?
MaxwellBuchanan, Nov 11 2015
  

       or become?
Ian Tindale, Nov 11 2015
  

       Asymmetric lives matter.
FlyingToaster, Nov 11 2015
  

       [MB] The cartridge case is designed to fit snugly in the chamber and when fired the chamber handles the pressure pulse not allowing the case to expand. If a round is heated as in a house fire there is no explosion, just a little pop because there is no barrel to contain the expanding gases pushing the bullet forward. The bullet pushes out of the case but only with enough force to dent the inside of a pan if heated on a stove. The powder burns uncompressed. So if your neighbor has the 10,000 rounds everyone should have on hand, don't worry if his house catches fire.
cudgel, Nov 11 2015
  

       //there is no barrel to contain the expanding gases pushing the bullet forward.//   

       Yes, point taken. But if the case were longer (extending a couple of inches beyond the bullet), would it burst for want of the surrounding chamber, or would it fire the bullet as well as a very short- barrelled handgnu?   

       And, if it *would* burst, how much heavier would it need to be in order to *not* burst? Clearly a gun barrel is engineered to survive repeated use; would a slightly-thicker-than-normal case survive one use?
MaxwellBuchanan, Nov 11 2015
  

       Ooo! Ooo! Wrap the case in piano wire!   

       I think my neighbor should have had half as many bullets and a fire extinguisher or two. Watching him fight the fire with his guns was worth the price of the bulletproof glass for my front porch.
bungston, Nov 11 2015
  
      
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