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The AR for Plastic Brick Lovers
You're going wait, wait, wait. Even if you WANT to build a gun out of plastic blocks, a gun made out of plastic is just a toy. Even that 3-D printed single shot is just a single shot toy.
Ah. Let's talk about the AR-15, designed by Eugene Stoner in 1958. In the conventional fashion, he attached the barrel to a metal receiver that the bolt slides back and forth in. The bolt is roughly a cylinder that slides back and forth on most guns, and has little hooks and lips to pull the fired case out of the barrel, and push the new one in.
What Mr Stoner did differently in the AR was use TWO receivers - an UPPER receiver, that the barrel screws into and the bolt slides in, and a LOWER receiver, that holds the trigger, the hammer, the magazine, and the stock. Since the magazine well (what the magazine slides into) has a nice flat surface, Colt ended up putting the serial number on the LOWER receiver when they began civilian sales in 1963.
In the 1980's, it became popular to build one's own AR, using parts from various manufacturers, and at some point, the BATFE (who regulates guns in the US) made the decision the LOWER receiver was the actual gun. That is, you can buy barrels, triggers, stocks, and the UPPER receiver all day long off the interwebs, but you can only buy a new LOWER receiver from a Federally licensed gun dealer - unless you make one yourself.
So it turns out, an AR lower is just a hunk of aluminum with certain holes in certain places. It doesn't weigh very much. Any reasonably competent machinist can make one - and they do. You can even make one at home, if you have a $500 Chinese mill. There has been an explosion in companies that produce AR lower receivers.
About that plastic thing - in 2000, Cavalry Arms begin production of a plastic AR lower receiver with an attached plastic stock. They attached the stock, because they had discovered a weak point in the AR lower, which they reinforced by making the butt stock (the back end) of the gun a single piece with the lower receiver. All the other regular AR parts fit on the Cav Arms lower receiver - triggers, magazines, upper receivers, barrels, etc.
So - by 2000, you had 4 choices if you wanted an AR. You could buy a complete new rifle from a gun dealer, or a used one from someone who had. You could buy just an aluminum AR receiver from a gun dealer, and buy all the other parts online, and build it yourself. You could MAKE an AR receiver from a hunk of aluminum on your $500 Chinese mill, and then bolt on all the other parts. Or, you could buy a PLASTIC lower receiver from your gun dealer, made by Cav Arms, and assemble it yourself.
Enter Defense Distributed. They recognized you could make your own lower receiver at home. They recognized that the AR lower could be made of plastic. And they realized with the correct design, one could 3-D print a plastic lower on a 3-D printer. So as of 2013, you have a fifth choice if you want an AR - you can PRINT a plastic lower.
So what does this have to do with plastic bricks? Easy. If you don't have a $500 Chinese mill & a $100 hunk of aluminum, or a $400 3-D plastic printer, it's off to the gun dealer with you, right? Maybe. Or maybe you can dig into your kids' toy box, sit at your kitchen table, and build an AR lower out of the plastic building bricks you already have in your house.
So - we offer you a sixth choice in the route to owning an AR. You don't need a $500 piece of equipment to make aluminum chips or plastic shapes, and you don't have to walk down to your gun shop. You need some ABS glue, some time, and a lot of plastic bricks and patience.
A nice circular link