There’s an area in the cascade range (western US, specifically oregon) that is a giant field of knapped obsidian, that was used as a training ground for young knappers, as well as a trading ground to trade knapped obsidian that has been found all over the western US. Not just miles, but many many miles. I’ll see if I can go find a link.

Hooooo boy. There’s a lot you can’t do. If you have a rifle (that uses a ‘rifle’ round as opposed to a pistol round), your barrel must be over a certain length. But if you have a “rifle” that is chambered in say 9mm (a pistol round), doesn’t matter. Barrel could be 4 inches long. But then it can’t have a stock. So you have a “wrist brace” (read:totally not a stock I promise) instead. There’s a bunch of wacky shit the atf and congress have come up with.