Everything but the barrel and springs are 3D printed plastic.  Below is the assembly video, so you can probably just skip through it if you don’t have 10 minutes to spare:

Very nice.  Notably cool that he’s used a 3d printed AR-15 lower receiver with a magwell insert to accept 9mm magazines of his own design.

Here’s a test fire video.  I love the HK style charging handle:

Thoughts?  Do you see the current laws which let people build firearms for personal use being changed because of 3d printing?  Has a crime ever been committed yet in the US with a 3d printed gun?