Why go to brass?
AR receivers (uppers and lowers) are typically made of 7075 aluminum. You could make them out of just about any aluminum and they’d work. The 7075 alloy is just stronger than other aluminum alloys.
The melting point of aluminum alloys that would be useful here (6061 or 7075) are in the range of 900 to 1100+ degrees F. Brass alloys melt up in the high 1600’s to low 1800’s.
What many AR fanboys don’t realize is that, to those of us who work on old-fashioned guns made of steel and wood, AR’s are already effectively made from pot metal and plastic.
AR
The important parts are made of steel.
For a first time process you could cast the lower out of melted aluminum beer or soda cans. But its not a high strength aluminum allow. Obviously almost any metal would work that can be melted. And anyone can argue themselves blue which is better. But if it fired at least a mag full its a success. Even if its heavy, chunky and full of voids if it houses the important parts and allows them to work then its a success.
The cat is out of the bag, its pregnant and its going to propagate explosively. I visit firearm forums a lot and its amusing how many internet ego experts are popping up claiming it won’t work, it will be ugly, they who make their own are not of the elite bling crowd, yadda yadda yadda.
I see history here when during the Revolutionary war people were making their own rifles, its time we do it again.
LLS