[AWildC182]

Guns are weird because to be effective they typically need to be rifled. You can obviously make a shotgun with some home depot pipe but the pressure bearing components of a gun can't be 3D printed. Even with 3D metal printing, you still need to machine the parts to final tolerances and your average garage setup is not remotely capable of rifling a barrel. Hence, when you hear about people 3D printing an AR, they're making the lower receiver which is both a trivially simple part, largely non load bearing, and also due to US law, the legal "gun" part of the gun. In most other countries the pressure bearing parts are the controlled items as those are the hardest to manufacture. In the US you can just buy an upper with the bolt, barrel, and chamber without a background check and manufacture the controlled lower however you want to obtain a complete rifle.

I guess this is all a long winded way of saying the 3D printing panic is both right and wrong but neither side is looking at it in a factual way.

[apr]

You can rifle a barrel in your garage. Search youtube, there are DIY videos.

Btw, you need a rifled barrel to make accurate shots at long-ish distances. For close quarter combat a submachine gun with a smooth bore would do quite well. Something similar to this: https://en.wikipedia.org/wiki/Borz. Any machine shop can crank those out in numbers.

[AWildC182]

I was a bit simplistic given that I didn't expect all the HN gun experts to come out of the woodwork on this one but I'll bite :)

Yes, you can get by with a smooth bore but "long-ish" here is significantly less than buckshot range. To get really nerdy, if volume of fire (submachine gun) is going to replace accuracy, the difficulty in creating a reliable magazine dwarfs the difficulty in rifling and while I haven't tried, I don't think 3D printing has the tolerances to solve that...yet.

Yes you can rifle a barrel in a garage but you need real machine tools as well as some very specialized tools that you'll need to either acquire or build which kind of adds steps beyond "have machine tools" -> "make gun"

[apr]

To crudely rifle a barrel you just need a press. Or you can make a machine like this: https://www.alloutdoor.com/2017/04/17/watch-homemade-barrel-.... I once saw a video of a machine which did not require any machine tools, you'd just make a guide and then manually cut the riflings. All you need there is a lot of patience.

For these designs you also do not need 3d printing at all. You just need suitable pipes, or sheets of metal that you bend and either weld or use fasteners to make the receiver. You are right though, designing and building reliable magazines is probably going to be one of the things that require a lot of attention to details.

There are books that have full blueprints for crude SMGs, here is an example: https://www.amazon.com/Do-yourself-Submachine-Gun-Lightweigh...

[exoesquitur]

Depending on the magazine dimensions (single stack is hard) Reliable magazines can be largely 3d printed, as can the follower and the jigs used to bend piano wire into proper springs. The 3d.printed.mag will usually have less capacity than a metal one though.

[bsder]

> your average garage setup is not remotely capable of rifling a barrel.

I'm going to argue the point. Yes, your average suburban weekend warrior won't have the stuff. But if you are even slightly into machining, you almost certainly can.

Practically every machining magazine will have at least one article about rifling in every issue.

Yes, you need a metal lathe and some tooling. Those are neither rare nor that expensive--and very old lathes and tooling work just fine.

The biggest problem a machinist always has is space for the equipment.

[_jal]

Amateur machinist here. I don't care about guns, so it would probably take a mistake or two, but I have zero doubt I could make a rifled barrel on the tooling down the block at my local makerspace. It isn't hard at all. (QC and repeatability are different topics, I'm not talking about commercial manufacturing.)

I can't do it in my garage, because I don't have one. My machines have to go up stairs in an urban walkup, so they're too small, and as mentioned, I have no interest in making guns anyway.

But yeah, a lot of people have both the skill and the means. Remember that people started making rifled barrels in the 1500s, a little while before we had CNC or overnight commercial-grade metal delivery.

[6nf]

All you do is make a die, harden it, and then carefully force it through the barrel? I guess?

[AWildC182]

Yea, that's a fair point, it's not insurmountable. I responded to apr mentioning something similar but ultimately the point I'm making is mostly that the upper requires a small machine shop filled with mostly commodity tooling and the lower requires a file and a drill press or a cheap 3D printer.

[roel_v]

At work so can't watch videos on rifling a barrel, but can this tooling also be DIY'ed? I imagine rifling is 'just' a matter of using a very thin, very long cutter on a suitable lathe, but then I would think it would be pretty hard to make such a cutter yourself.

[bsder]

> At work so can't watch videos on rifling a barrel, but can this tooling also be DIY'ed?

There are a zillion videos on YouTube about this.

The hard part isn't the rifling, it's cutting the bore. After that, you can "just" push a rifling button through it and it will cut the rifling.

[convolvatron]

haven't looked at rifling, but making single point boring cutters for a lathe isn't at all hard. you can just screw a carbide cutting insert onto any old piece of steel.

seems like you'd have stiffness problems for long barrels (?)

[dsfyu404ed]

You could make a push broach that holds an insert (or make it out of HSS then press it through the barrel.

[mirimir]

True, but fin-stabilized sabot rounds (~darts) for the 12 ga shotgun are damn impressive.

https://www.youtube.com/watch?v=WGzgbXCrWHQ

[riskneutral]

> your average garage setup is not remotely capable of rifling a barrel

Ehhh ... you talk a lot about 3D printing, but that’s not the only tool that people have in their garages. A huge number of people have metal lathes in their garages. I happen to have a small, CNC controlled metal lathe and mill in my garage. The whole setup cost me about the same as a high quality, rapid prototyping 3D printer (<4000USD). I am pretty sure I could make a firearm, in my garage, including rifling, if I was determined to do so.

Personally I have no desire to build my own firearms, because it’s illegal to do so in my country and it’s also extremely dangerous. But in many places in the US it does appear to be legal.

[tomatotomato37]

I think the reason for going after lowers is because that's where, in AR pattern at least, the majority of components for auto-firing are mounted, whereas the upper may just have an extra notch or two etched in the bolt.

[rtkwe]

No it's because the lower is legally the gun, because it has the trigger and hammer assembly in it. The whole rest of the upper half of the gun can be ordered online and shipped right to your house because it isn't legally a gun or the critical components.

[6nf]

Very different in Australia where every part of the gun is restricted. You can’t buy a single gun part and you certainly can’t buy ammunition without a license.

[AWildC182]

The auto sear (auto-firing part of the lower) is just a little lever hinged on a pin that blocks the hammer from moving momentarily. The two cuts that it interfaces with in the upper are somewhat more complicated.

[tomatotomato37]

I thought it also required some sort of twisted wire pin that interfaces with the sear and hinges off something built into the upper.

The majority of my firearm knowledge comes from that world of guns puzzle game so I'm probably very off on something, but I do remember there was a lot of going on in that area of the gun

[dsfyu404ed]

Maybe you're confusing it with the fact that you can make a ghetto drop in auto sear out of a bent coat hanger?

Google "drop in auto sear" eventually you'll find something that explains the sequence of events of the trigger mechanism in sufficient detail.

[dilyevsky]

Dunno if it qualifies as “sophisticated“ but original AK is designed to be made from like a piece of sheet metal and others pointed out you can rifle a barrel in your garage.

[billh]

It has been demonstrated that you can fashion an AK out of a typical gardening shovel. https://www.northeastshooters.com/xen/threads/diy-shovel-ak-...

[crystalPalace]

There's always the classic shovel AK: https://www.northeastshooters.com/xen/threads/diy-shovel-ak-...

[AWildC182]

Sheet metal is actually harder to use than milled parts, it's just cheaper for mass production. The original AK was a milled receiver which they switched to stamped for subsequent iterations. Stamping metal with high accuracy is very hard and requires very special tooling.

[dilyevsky]

Sorry, no. It is cheaper in every way possible. The lower receiver is literally metal box with holes in it. You can hammer it out by hand and cut to size with a dremel. The most challenging parts will be smaller pieces (hammer, bolt etc) and all the tubing for the gas trap system (that one will actually require some welding). That’s if you want to build it entirely from Home Depot materials and tools for some reason (in the US only receiver is legally a “weapon”).

[dsfyu404ed]

> Stamping metal with high accuracy is very hard and requires very special tooling.

Only if you want to crank them out by the millions. As the "shovel AK" clearly demonstrates you can get it done more easily if you don't need to produce them at scale.

[anth_anm]

AK are harder to make at home because it's sheet metal. Requires welding and other harder work.

Vs buying an 80% blank, drilling a few holes, and then routing.

[6nf]

I see these 80% kits online that even includes the tooling you need to complete it. It’s so simple anyone could do it.

[dilyevsky]

If compared to commercially available 80% lowers for ar, sure