If you buy it as a registered destructive Device, don't buy it as a 37 mm or as a firearm. Guys who bought them as without 40 mm barrels are finding out barrels are not always available.
I just sold my spare barrel & some chalk rounds to a friend of mine a few days ago. The WTB ads on sturmgewehr.com are popping up pretty regular. Before my buddy bought mine I offered to another guy @ $50.00 over MSRP, but there was no S&H or taxes asked for. My friend drive 2 hours one way, but we ate a steak & he bought the chalk rounds. I even let him have the nice crate.
Thats what I'm seeing, only receiver i can find is a rail mount, but no barrels.
I think i want to stick to the barrel mount anyways