You can just buy a standard issue copper pipe for plumbing and use it as the barrel, maybe put some vaseline inside to reduce the stress on the somewhat weaker copper material. Or buy a standard issue household hardened steel printer, which will soon be available. If the plastic printers can also print carbon materials or nanotube barrels then the government can finally be overthrown as well.
The future is bright, mostly from the gunfire and explosions.
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