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In Canada, a 3D-Printed Rifle Breaks On First Firing
Not all 3-D printed guns can encounter the smooth, uneventful success of Cody Wilson's Liberator; Daniel_Stuckey writes with this excerpt: "A Canadian has just fired the first shot from his creation, 'The Grizzly,' an entirely 3D-printed rifle. In that single shot, CanadianGunNut (his name on the DefCad forum), or "Matthew," has advanced 3D-printed firearms to yet another level. Sort of: According to his video's description, the rifle's barrel and receiver were both damaged in that single shot."
Rifle cartridges tend to have quite a bit more power than pistol cartridges.
Chamber pressure:
.45 ACP maximum pressure 140 MPa / 21,000 psi
Rifle: 7.62x51mm maximum pressure 415 MPa / 60,191 psi
Rifle: 5.56x54mm maximum pressure 430 MPa / 62,366 psi
Pistol:
Pistol: 9x19mm maximum pressure 235 MPa / 34,084 psi
Pistol: 9x17mm maximum pressure 148 MPa / 21,500 psi
IIRC, the 9x17mm (.380) was used in some earlier 3D printed pistol tests with limited success.
Most people receiving medical treatment after being shot by a pistol will live. Mortality is much higher for those shot by a rifle.
much of left-wing thought is a kind of playing with fire by people who don't even know that fire is hot - George Orwell
That's the thing - I doubt there's a 3D-printable plastic out there now which could last for one rifle shot, at least outside of sheer luck.
The length of the rifle barrel is what'll kill it. A pistol dumps its internal pressures quickly - the short muzzle doesn't have to hold the pressure for more than a millisecond or two at most. A rifle on the other hand? The longer the barrel, the longer that period of time which the barrel has to hold the higher pressures. Most rifle cartridges also contain a slower-burning powder (to keep pressures at least somewhat constant as the bullet travels down the barrel), which only exacerbates things from a design perspective.
From an industrial perspective, any plastic barrel that doesn't hold up to insane tolerances (at least 3x max pressure) and do so for a very long time? Begging for a lawsuit that'll bankrupt your company, guaranteed. Also, there's no real economic incentive to make plastic barrels commercially - steel is way cheaper to acquire, machine, and temper. Now there are some specialized and niche applications (spies, special ops/forces, whatever), but they don't justify the costs.
Hobbyists OTOH don't have that kind of pressure or limitation - they're just doing it because they can.
Quo usque tandem abutere, Nimbus, patientia nostra?