I saw a post about people sharing 3D designs for weapons and parts.
Here is the discussion about it on the site that hosts the designs:
Deadly Weapons on Thingiverse
Lower receiver design:
AR-15 Lower Receiver by KingLudd - Thingiverse
AR-15 Rifle Magazine by crank - Thingiverse
I doubt that the plastic can handle the pressure, but as the technology improves, it will become feasible.
What are your thought about the ability to literally print firearm components at home?