Barrels, springs and working parts are the only thing that needs to be made out of metal. also 5.7x28 is a terrible calibre. Its pistol ammo, that at best has the knockdown and kick of 9mm, and at worst is an expensive non-standard cartridge. Its far overhyped, and far overrated.
It should be noted that Glocks' slides are not made of polymer either. Additionally, 5.7x28 is terrible if you're looking for a large bullet. It has large capacity and is also armor-piercing, so it fills a niche that standard 9mm doesn't really satisfy. I do agree with you that it's overhyped and expensive, though.
And hey, it's a plastic gun.
No, it's not. It's not even close to that. It's a plastic lower receiver with the rest of the gun being not plastic.
As far as the ATF is concerned, an AR-15 lower receiver is a gun because it is the part of the gun that is serialized. Of course, your statement is true if you're arguing above the legal authority of the ATF, an organization that considers shoelaces to be machine guns.
Aaaannnnnd you lost me.
Werner von Braun.
I don't know about you, but when I was in third grade I didn't have any heroes that knowingly used Jewish slave labor.
/* Halley */ (Halley's comment.)