Idea for easier 80% lower

[Groyper]

So I have an idea, you take a plug made of glass that has been modeled in dimensions of buffer tube threading, fire control pocket, holes etc, then you pour steel/aluminum around it, having the proper dimensions to it, then after the customer buys the lower and uses some sodium hydroxide (drain cleaner) to dissolve the glass plug, creating a ready to use lower.

As I understand it, the melting point of the glass is higher than steel/aluminum so the plug will not melt, I assume the only issue here would be the shrinkage from the metal contracting as it cools?

Any unforeseen issues with this idea?

I assume the ATF will give it a no go because they are dicks?

[HeruMew]

Depends.

If you applied for approval without all the explanation, it probably wouldn't be looked at too hard.

But I could totally see them going: "So break the glass and it's a firearm? Seems too easy." Without having a good grasp of it anyways.

[Groyper]

Depends.

If you applied for approval without all the explanation, it probably wouldn't be looked at too hard.

But I could totally see them going: "So break the glass and it's a firearm? Seems too easy." Without having a good grasp of it anyways.

Well you could "break it" but it is still there, and likely will be as solid glass in such a configuration would be very hard to break and remove, that is why development via chemicals was selected as the desired method.

But then again I thought of this idea around 2 days ago so its a bit in the air.

I don't think sodium hydroxide dissolves glass.

Well guess I was wrong but next question is what does it do to aluminum.

"Glass is one of the least reactive substances known to chemistry. It is the standard container material for almost all lab chemicals because it's so inert. But there are a couple of substances that have strong reactions with glass. Sodium hydroxide, aka solid drain cleaner or lye, can easily be stored in glass as a solid, but when molten, it reacts violently with glass and can actually dissolve it away! So, the next time you clog up your drains with broken glass beakers and flasks, rest assured your household drain cleaner has what it takes."

Sodium aluminate is also formed by the action of sodium hydroxide on elemental aluminium which is an amphoteric metal. The reaction is highly exothermic once established and is accompanied by the rapid evolution of hydrogen gas. The reaction is sometimes written as: 2Al + 2NaOH + 2H2O → 2NaAlO2 + 3H.


So I assume we need the proper alloy, to prevent this, or maybe just use steel.

I am also not sure why no one else has done this before.

[Leonidas24]

So here's the thing: 1) lowers are forged, not cast. Regardless I wouldn't touch a cast AR lower if it was the last on earth. 2) If you're casting aluminum around glass it doesn't matter what the melting temp is, the glass is going to crack or expand, especially with small details like FCG and selector holes. 3) Most glasses are extremely inert when they encounter NaOH even in extreme concentrations (as an aqueous solution.) As mack7.62 pointed out above molten NaOH will react with glass, but also consider the melting point of NaOH is north of 600 degrees Fahrenheit, well into the range Aluminum begins to become pliable. It won't work. Don't let the good idea fairy bite too hard next time.

[MegademiC]

So here's the thing: 1) lowers are forged, not cast. Regardless I wouldn't touch a cast AR lower if it was the last on earth. 2) If you're casting aluminum around glass it doesn't matter what the melting temp is, the glass is going to crack or expand, especially with small details like FCG and selector holes. 3) Most glasses are extremely inert when they encounter NaOH even in extreme concentrations (as an aqueous solution.) As mack7.62 pointed out above molten NaOH will react with glass, but also consider the melting point of NaOH is north of 600 degrees Fahrenheit, well into the range Aluminum begins to become pliable. It won't work. Don't let the good idea fairy bite too hard next time.

All of this. It wont turn out how you think.
Milling them is way easier and safer.

[Groyper]

All of this. It wont turn out how you think.
Milling them is way easier and safer.

BUT I DONT WANNA!

So here's the thing: 1) lowers are forged, not cast. Regardless I wouldn't touch a cast AR lower if it was the last on earth. 2) If you're casting aluminum around glass it doesn't matter what the melting temp is, the glass is going to crack or expand, especially with small details like FCG and selector holes. 3) Most glasses are extremely inert when they encounter NaOH even in extreme concentrations (as an aqueous solution.) As mack7.62 pointed out above molten NaOH will react with glass, but also consider the melting point of NaOH is north of 600 degrees Fahrenheit, well into the range Aluminum begins to become pliable. It won't work. Don't let the good idea fairy bite too hard next time.

So any way a cast AR lower would work?

[mack7.62]

I don't think sodium hydroxide dissolves glass.

Well guess I was wrong but next question is what does it do to aluminum.

"Glass is one of the least reactive substances known to chemistry. It is the standard container material for almost all lab chemicals because it's so inert. But there are a couple of substances that have strong reactions with glass. Sodium hydroxide, aka solid drain cleaner or lye, can easily be stored in glass as a solid, but when molten, it reacts violently with glass and can actually dissolve it away! So, the next time you clog up your drains with broken glass beakers and flasks, rest assured your household drain cleaner has what it takes."

[Coyote bulldozer]

What's your objection to just doing it the normal way with a jig kit? By far the easiest method to finish 80% lowers sans a mill is the jig and hand held router! Last year around my birthday me and my buddies had a "milling party" and cranked out 5 complete lowers in an evening (hell by the final one we had the process down and completed it start to finish in under an hour).

By comparison my other buddy is in the hobby of casting aluminum ingots, it takes several hours just to melt enough aluminum cans in his small hobby crucible to cast one single cupcake pan sized ingot, never mind melting enough to cast a whole AR lower... I've never personally priced hobby grade aluminum casting equipment but said buddy was bragging at work how he picked up his new (again very small and hobby-only grade) crucible for $600 so it seems the typical jig/router/drill press route is probably the cheaper route as well (you could pickup the jig with some 80% blanks AND a router for under the price of JUST the crucible and then you'll still need to buy / build the molds and everything else involved with casting).

There are no advantages to this idea...