Disclaimer: This article will discuss the process of completing an AR-15 80% lower with common tools found in most hardware stores. A provision in the Gun Control Act of 1968, 18 U.S.C, Chapter 44 states that an unlicensed individual can make a firearm for personal use, but not for the intent of sale or distribution. Said firearm must conform to N.F.A standards and you must be legally able to be in possession of a firearm. Should you desire to create a Short Barreled Rifle or a Machine gun the BATFE is going to require additional paperwork. If down the road you desire to sell your rifle you will have to put a serial number on it and transfer it via a Federal Firearms License holder. If you never intend to transfer or sell the firearm it must be destroyed upon you giving up possession of the firearm. Granted this is the generally accepted translation of 18 U.S.C, Chapter 44 you should still check local and Federal laws before attempting to build your own personal firearm. Technically you can sell a rifle you have made but you cannot simply make a rifle then immediately decide to turn around and sell it.
If you have not already, read Part 1 here.
Welcome to Part II of the Billet Rifle Systems 80% build! This article will discuss the actual milling process of an 80% lower as well as some tricks, tips, pitfalls and general observations in finishing an 80% Ar-15 lower receiver. Once again I would like to stress the use of eye protection. I would also like to mention that if you are using a drill press I do not advise using it like a milling machine. Once the mill bit is making contact and cutting the metal it is generally not considered a good idea to put lateral stress on a bit (Moving along the X and Y planes). If you plan on using a drill press to finish an 80% lower you are simply going to be making hundreds if not thousands of cuts along the “Z-axis”. Even though I am not using a milling machine I will be using the words “mill”, “drill” and their derivatives interchangeably. When I mention to “go slow” this does not pertain to the speed (RPM) of the drill press. It pertains to how fast the end mill bit is sunk into the aluminum. Due to the size of the pictures if you need to see something in greater detail simply click on the picture. The host will load a more detailed picture. Let us get started!
Milling out the last 20% of the Billet Rifle Systems lower receiver was very challenging. There is no question that an 80% lower can be successfully completed using a drill press. If I were to undertake this project again I would invest in a milling machine or a lathe. A milling machine would allow cleaner work, mitigate tool marks, and generally speed up the process. If you intend to finish an 80% lower using a drill press look for a steel jig set. Due to the vibrations of a drill press I made unwanted contact with my jig and my lower receiver several times removing a fair amount of aluminum. I don’t believe this would be a problem had I used a milling machine or a lathe. When drilling, try to position the aluminum as close the the mill bit as possible. This will shorten the area the mill bit has to travel and it will mitigate vibration from the drill press. I intend to get the receivers hard coat anodized in the very near future. Since there are a lot machine shops that cater to the Defense Industry here in Albuquerque, it should prove easy to find a local shop to do a Type III, Class 2 hardcoat anodizing that conforms to MIL-A-8625 specification.
At present I am working on the third part of this article set. Part III will post in several months and will feature a complete rifle build. Many of my readers can surmise that as an Armorer I am a slave to technical data packages. A technical data package is a large set of data that specifically states how a rifle should be made. Every military firearm ever procured by the United States government in recent history has a technical data package or manual. Granted the Colt technical data package is Colt property, the military has leaked it on several occasions. A quick Google search will give you an idea concerning the proper material and processes necessary to build a military specification/military grade rifle. I believe that guns should be built to a military grade of quality. Due to recent market and political trends there are a lot of poorly made rifles flooding the market. Said rifles are being built with substandard materials. These rifles will further proliferate the myth that the Ar-15 platform is unreliable. My fellow armorers and I are seeing trends concerning broken bolt lugs due to improper metallurgy as well as carrier tilt, broken disconnectors, bent trigger and hammer pins due to piston retrofit kits. As suppressors become more common, guns that do not have a method for adjusting gas flow are being prematurely worn out. Billet Rifle Systems manufactures military grade 7075 aluminum receivers…I was given a 6061 lower receiver to test…which is not military grade. I only trust my life to military grade weapons; however, I may build a training rifle or a hunting rifle with my test lower and run it hard. As long as consumers value form over function there will continue to be sub standard rifles; however, these rifles will still need to be overhauled, maintained, fixed, and upgraded. Maintenance schedules are common for military spec/military grade rifles, but my fellow armorers and I are in desperate need of data concerning maintenance and part longevity of rifles that are not military grade. It’s safe to assume that Part III will feature a non military grade rifle that I will use to gather data concerning parts ware and maintenance schedules. Who knows….Eugene Stoner’s design, even when not built to The Standard, may surprise me!
Thoughts, comments, gripes and humor are welcome in the comments below! Feel free to contact me if you have a question!