The DIY craftsmen at FarmCraft101 melted down a bunch of aluminum cans in his backyard to get the raw materials for an AR lower.
Nothing really high-tech involved. He melts the cans down in his foundry furnace crucible then pours the molten recycled aluminum into a plywood and sand mold box that he builds.
Cutting off the sprues and machining out the billet, he threads and mills until he gets a relatively mil-spec receiver. Drop in a LPK then attach an upper, and it’s ready to rip some rounds through.
Sure, you need a furnace, a lathe, a saw and some metal trades skills, but in the end, as long as you have a sweet tooth or a beer belly, you are only 23 12-packs away from an AR lower.