0% receivers

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Netpackrat
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Re: 0% receivers

Post by Netpackrat »

HTRN wrote: Tue Jan 18, 2022 10:41 pm Orrrr

Just make the lower from something else, like 416.
That'd probably be pushing the capabilities of the GG3 a bit, but while you are at it, you could also have it polished, engraved, and gold plated. :roll:

This is the modern equivalent of a homemade sten in 1948 Israel. Maybe worry about actual problems like where are you going to get the difficult parts in the upper if gun parts in general get restricted. You made the first lower by pushing a button. It gets worn or corroded, you do the same thing again for a replacement, assuming you've lived that long and you've actually still got it.
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Re: 0% receivers

Post by HTRN »

Netpackrat wrote: Tue Jan 18, 2022 11:04 pm This is the modern equivalent of a homemade sten in 1948 Israel. Maybe worry about actual problems like where are you going to get the difficult parts in the upper if gun parts in general get restricted. You made the first lower by pushing a button. It gets worn or corroded, you do the same thing again for a replacement, assuming you've lived that long and you've actually still got it.
If you're considering them disposable, just print a lower using a fdm printer and high strength filament, like polycarbonate or nylon. If you're going to consider lowers disposable, might as well use something cheaper than a 3k dollar gg.
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Netpackrat
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Re: 0% receivers

Post by Netpackrat »

HTRN wrote: Wed Jan 19, 2022 5:52 am If you're considering them disposable, just print a lower using a fdm printer and high strength filament, like polycarbonate or nylon. If you're going to consider lowers disposable, might as well use something cheaper than a 3k dollar gg.
I don't know if disposable is the right word. There's a difference between that and expecting them to have a high rate of attrition. My main point is that rather than gilding the lily, once you can make sufficiently durable lower receivers in whatever quantity is required, there are a lot of other parts that are probably more difficult to produce that could be subject to regulation or at the very least to tracking. If you were willing to settle for a blowback PCC/subgun AR, then that simplifies things a lot, but even at that not too many people have the ability to make a barrel or BCG. People are focused on lowers because that's what is currently regulated in the US, but the lower is far from being the biggest obstacle. As you point out by bringing up 3d printing.

The GG does seem expensive for what it does. OTOH I don't know how many other desktop CNC mills basically the size of a big toaster oven are out there.
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Vonz90
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Re: 0% receivers

Post by Vonz90 »

It would not be that hard to design a lower that works with lower grade aluminum. There are only a couple high stress points on it, mostly around pins, and that can be accounted for.

Still, one wonders to why. As NPR said, in a world wide SHTF scenario- who cares, in a gun hobby scenario there are lots of options for coatings.

I don't see myself doing it, but if I did I would probably anodize it as best I could at home and then guncoat over that.
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Re: 0% receivers

Post by blackeagle603 »

Would heat treating be helpful?
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Re: 0% receivers

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blackeagle603 wrote: Wed Jan 19, 2022 5:44 pm Would heat treating be helpful?
If you buy a chunk of something like 6061T6 or 7075T6 aluminum to make your receiver out of, it's going to come with as much heat treatment that it's practical to give. The hard anodizing that commercial receivers get will give it that last bit of surface hardness plus some protection against corrosion. You can do a Gunkote or Cerakote but I have always been leery of the baked finishes on aluminnum because you are starting to get into the range where the temper can be affected when you bake the finish. The gun painting industry doesn't seem to give a shit about that though. And it's not going to do anything for corrosion and wear at points where the steel parts thread into or wear against the aluminum receiver.

But again, while that may cause a gun to get sloppy or even corrode after a few years of abuse, it's a fairly low priority compared to more pressing needs like heat treated, pressure bearing parts, rifling, etc. In the US at least for the forseeable future it's mostly a gee whiz look what we can do kind of exercise anyway, since there are already so many commercially manufactured guns already out there in the hands of the militia.
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Re: 0% receivers

Post by Vonz90 »

blackeagle603 wrote: Wed Jan 19, 2022 5:44 pm Would heat treating be helpful?
I don't do aero stuff so maybe the aero guys can chime in, but at least in the part of the engineering word I live in, I have never seen a need for heat treatment of anything aluminum that I have designed. There are some alloys that can theoretically be heat treated, but it is not common.
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Re: 0% receivers

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HTRN wrote: Tue Jan 18, 2022 10:41 pm Orrrr

Just make the lower from something else, like 416.
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Re: 0% receivers

Post by blackeagle603 »

Yeah, only time (in my sphere) I've seen aluminum heat treated was after welding.
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Re: 0% receivers

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Vonz90 wrote: Thu Jan 20, 2022 3:07 pm
blackeagle603 wrote: Wed Jan 19, 2022 5:44 pm Would heat treating be helpful?
I don't do aero stuff so maybe the aero guys can chime in, but at least in the part of the engineering word I live in, I have never seen a need for heat treatment of anything aluminum that I have designed. There are some alloys that can theoretically be heat treated, but it is not common.
Some of the most common alloys are heat treated. Say you make something out of 6061T6, the "T6" is the temper designation. It comes from the mill with all the heat treatment it will ever need (or benefit from). If you ever get your hands on a piece of 6061T0, you will be able to tell the difference, especially in thin sections. In aviation we're usually working with 2024. The normal way it is supplied is in some form of T3 or T4 temper, which again is the heat treated state (with some minor differences between the two and other designations besides). Occasionally we will need to make a repair part with some significant forming operations which would result in cracking if done to material in the T3/T4 condition. In those cases, it's common to start with T0 material, do the forming operations, and then have the part sent out for heat treat. The T0 material is very soft and wouldn't be useful for much, aviation or otherwise.

Other alloys are not heat treatable, and reach their full temper through work hardening. These are common in marine environments for example (5083/5086, 5052), and sometimes in aviation for non-structural parts (tanks, fairings, etc... Generally 3003 or 5052). The door, bonnet, and boot lid skins of my MGA are made of 5052. Part of the panel beater's art is to arrive at or near the desired hardness at the end of forming operations, since the only heat treating process available with such alloys is annealing. Depending on what you are making, and how severe the forming operations, you might need to anneal several times before the part is completed. You don't want to have to anneal again as you are just finishing because then the part will not have its full possible temper, but if you don't anneal enough you could get a crack somewhere in the process.
blackeagle603 wrote: Mon Jan 24, 2022 8:45 pm Yeah, only time (in my sphere) I've seen aluminum heat treated was after welding.
The reason for that, is if you started with something like 6061T6, after welding you might have something closer to T2. That might be strong enough depending on the application, but if heat treating is specified, the purpose is to restore the temper that the material originally had prior to welding. Some alloys (such as 2024) are not generally considered weldable.
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