This is a brief overview of how my two-part printed Lower Receiver is assembled into a fully functional Lower Receiver.
I’m going to assemble an AR-15 Lower Receiver from parts. The lower Receiver is the part of the AR(Armalite Rifle)-15 civilian firearm that contains the fire control group, the magazine well, and attaches the stock to the Upper receiver which holds the bolt and the barrel. On its own, the Lower Receiver is hardly recognizable as a firearm. One would be more likely to confuse an upper receiver by itself for a firearm than a lower. But the Lower Receiver is the part on which the serial number is stamped, and of all the distinct components of the complete rifle, this part is legally considered to be ‘the gun’ even without all the other parts. Thus, a firearm transfer is required to just this part from anywhere outside my state(legally, you’re buying a firearm from out-of-state). But one is legally allowed to make one of these for personal use(not with intent to sell) without needing a firearm manufacturer’s license from the BATFE. It is less expensive to print my own than to buy one.
These are the parts I will be using.
After printing both parts of my two-part lower Receiver, I must remove the support material which I added to the models to facilitate printing. This support material was added by me in the model itself, so the model was sliced and printed without automatically-generated support material. It was only necessary in a few specific areas, and milling material out of every qualifying cavity is very time-consuming. And unnecessary with my modeled support.
After the support material is removed, the magazine well is tested for fit. The printed model has artifacts from printing, and interior spaces seem to be slightly undersized after printing.
Once magazines fit properly in the well, the magazine catch is installed.
After the magazine catch is installed, the official guide says to do the bolt stop, but I did this a little out of order. It doesn’t really matter. The fire control group is next.
Next up is the front pivot pin which holds the Lower Receiver to the upper.
Now that the rear part of the lower is assembled, I can install the safety in the fire control group.
The safety goes into the hole behind the trigger, just in front of my two-part attachment bolt.
Some would consider the lower to be complete at this point(minus the handgrip). You may notice a captive nut in the handgrip area. This nut I added to my printed lower after stripping the plastic threads of my previous versions of printed lower receiver.
Now I will add my combined grip and stock to the lower and have it fully completed.