The future is NOW

3-D printers have been around for a while now. Some of them can make solid metal objects by "printing" metallic powder and then sintering it to make it solid.

So now, we can print our own guns at home:
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AR-15 Lower Receiver by KingLudd

Description Print at YOUR OWN RISK, Neither the creator of this object nor thingiverse.com is responsible for anything that happens because you printed this object!

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Seen at Roberta's