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."

Comments

I still see a market ....

[therealkevinkretz]

ACME firearms, supplying evil coyotes for decades

Re:I still see a market ....

[Penguinisto]

Heh - what else did they expect? Rifles keep pressure for longer periods of time (as the bullet travels down the longer barrel), increasing the chance for materials failure. Cheap plastic is not an option here, campers.

7,000+ psi for a .22LR is nothing to screw around with for the relatively sustained period of time the bullet travels down the barrel (let alone the 65,000+ psi you can generate in, oh, a .338 Win Mag.)

Re:I still see a market ....

[Penguinisto]

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.

Re:I still see a market ....

[Intrepid imaginaut]

The cheapness of the plastic isn't really an issue - trying to pretend it has the same properties as steel is. You could make a fairly workable rifle with 3D printing but you'd have to adjust the design to match the materials used, in other words it would have to be bulky enough to make a WH40k Space Marine's double bolter look like a flimsy toy in comparison. Two to three inch thick walls on the barrel would make it a lot more durable, although melting becomes your problem then.

In Canada?

[Black Parrot]

What happens if you try it somewhere else?

Big surprise

[cold fjord]

Rifle cartridges tend to have quite a bit more power than pistol cartridges.

Chamber pressure:

Rifle: 7.62x51mm maximum pressure 415 MPa / 60,191 psi
Rifle: 5.56x54mm maximum pressure 430 MPa / 62,366 psi
Pistol: .45 ACP maximum pressure 140 MPa / 21,000 psi
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.

Re:A new slogan

[HornWumpus]

They would humor you. Rednecks already own a number of real guns and would assume you were some sort of city idiot. Once they figured out that you weren't going to blow off your hand they would go home.

Re:Not to worry

[fuzzyfuzzyfungus]

Only a matter of time before the composites and process improve to the point where it will withstand these stresses.

Inconveniently, 3d printing techniques tend to make doing composites (properly) difficult. Extruder-based designs can use fiber reinforced feedstocks, if the usual parameter-fiddling is done properly; but doing that will mostly just serve to make the difference in strength between the continuous filament (relatively strong) and the bonds at the 'seams' where the newly extruded filament needs to fuse with the previous layer and any adjacent already-laid filament (absolute best case, these might be as strong as the continuous filament, almost always weaker, sometimes markedly so, depending on process control) even starker than it already is, since the reinforcement material won't extend throughout the part (as it does with injection-molded fiber reinforced parts).

Selective laser sintering, while classier, is similarly limited by the fact that the reinforcement material can't extend beyond the boundaries of the powder being sintered (and you can't make the powder particles larger without sending your resolution to hell).

(Now, in the hypothetical cyberpunk dystopian future, it might be possible to produce pre-woven carbon-nanotube/graphene/similar technobabble "sleeves" that would collapse down into easily concealable flat shapes (like a freshly ironed sock); but could be stretched over a simple form and impregnated with a polymer or epoxy to turn them into fiber-reinforced barrels quickly and with almost zero tools just before use, using the same basic techniques used for fiberglass or carbon fiber construction. Not obviously worth it vs. just smuggling normal guns; but it' be a cute trick.)