h a l f b a k e r yPoof of concept
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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.
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]
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Annotation:
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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. |
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Perhaps you could go to a ceramics workshop to make
Gyrojet barrels, and then 3D-print in plastic the rest of the
gun? |
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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. |
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[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). |
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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. |
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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. |
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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. |
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[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. |
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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). |
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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. |
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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. |
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Can't the casing be the chamber? |
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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. |
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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. |
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//Some part of the weapon has to act as the
chamber// |
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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? |
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I worry that the gun aficionados have become irregular visitors to the HB. |
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Are you worried that they're not regular, or that
they're visitors? |
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[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. |
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//there is no barrel to contain the expanding gases
pushing the bullet forward.// |
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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? |
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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? |
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Ooo! Ooo! Wrap the case in piano wire! |
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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. |
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