Before going further I will admit only slightly more than basic knowledge here. But how many recyclable plastics in common use have the structural properties needed for durable (even short term durable) mags and other gun components? And how many people have access to the equipment needed to recycle said plastics into
The materials are going to improve in the future. nanocellulose could be a game changer with one of these.
USDA Under Secretary Sherman Unveils Nanocellulose Production Facility
Posted by Rebecca Wallace, USDA Forest Products Laboratory, on August 3, 2012 at 11:57 AM
The U.S. Forest Service Forest Products Laboratory recently opened a $1.7 million production facility for renewable, forest-based nanomaterials. This facility is the first of its kind in the United States and one that positions the laboratory as the country’s leading producer of these materials, also called nanocellulose.
Nanocellulose is simply wood fiber broken down to the nanoscale. For perspective, a nanometer is roughly one-millionth the thickness of an American dime. Materials at this minute scale have unique properties; nanocellulose-based materials can be stronger than Kevlar fiber and provide high strength properties with low weight. These attributes have attracted the interest of the Department of Defense for use in lightweight armor and ballistic glass. Companies in the automotive, aerospace, electronics, consumer products, and medical device industries also see massive potential for these innovative materials.
"Here are the two most common plastics for these types of printers:
Acrylonitrile butadiene styrene
The gun, receiver, and magazines that Defense Distributed has created were I believe all printed in ABS plastic. It is very common. The recycling equipment you can build yourself for a few hundred dollars.
Here's one 3D company's materials list (they have spec sheets, other 3D printing companies have a similar list):