>>518534706 (OP)
reminder that gun control failed and you should:
if you can buy spent ammo casings, buy and hoard them, this is a major bottleneck
if you can't buy spent ammo casings (illegal, brazil/japan/south korea), get a 3d printer (you'll need it anyway) and a reisn filament, 3d print resin filament ammo casings for the caliber of choice (9x19mm)
if you can buy primers without a license, get small pistol primers, many of them, if you can't buy primers get antimony trisulfide (if you can't buy antimony trisulfide in its pure form, buy antimonite/stibnite, it's the same thing), potassium chlorate, shellac, alcohol, you'll need this to reload spent primers, if you don't even have spent primers you'll have to press them from thin metal or 3d print a special resin pole and cover it with solidifed H-48 compound you get by mixing antimony trisulfide and potassium chlorate (do not mix more than 30 grains it explodes violently)
if you can get nailgun blanks, get them, if they're not designed to misfire you will be able to extract the priming compound out of them and skip the antimony trisulfide, if you have them you can also extract fast burning nitrocellulose gunpowder from them
if you can't get nailgun blanks just mix black powder from freely available sulfur charcoal and potassium nitrate, black powder is more than enough to reach lethal muzzle velocities
if you can buy jacketed bullets, buy them, otherwise, buy a bullet mold and cast them from lead (LRN is even more lethal because its soft and will expand on its own)
this is all you need to make ammo
then you buy a 3d printer, either a 8mm (if you do ECM) or 9mm (if smoothbore) inner diameter 16mm outer diameter steel pipe, AR-15 FCG springs (bend your own if you dont have them), glock magazine (3d print if you cant buy it, you'll have to bend the magazine spring)
some metal rods for the bolt, you'll need an arc welder
a tube of jb weld or its alternative
some nuts and bolts and some other readily available stuff