Building an 80% AR 15

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    • #770
      LittleMan
      Keymaster

      Recently I decided to build an 80% AR 15 lower receiver. For those not knowing an 80% receiver is a block of metal (or plastic) which with only a little more machining and or drilling would legally (under US laws) be a completed firearm subject to regulations regarding acquisition and use. Until those final cuts and holes are made the block of metal is legally just that, a block of metal (or plastic) of no greater legal significance than any other paperweight. Not being a gun (yet) such items may be possessed by any person, sent through the mail or even given away as gifts.

      The 80% items are preforged or hewn into the rough shape of a firearms frame by the manufacturer, then sold to a consumer with those final cuts not done. They oftn come with instructions or drill/machining jigs to make transforming the rough shape into a functional firearm fairly easy. Easy enough so that whether you are a 10 year old, a convicted high school drop out felon, or even someone over 60, you can figure it out and have a working gun in just a few hours. Of course some basic tools will be required. With the jig I chose all that was required was a router, some drill bits, an end mill bit, and an electric drill. Oh yes, an allen wrench and a small phillips screwdriver.

      For my first 80% build although they are availlable for many firearms designs, to include 1911s, Glock pistols, Ruger rifles, Beretta pistols, etc., I chose to do an AR15 build. Inside the US the lower receiver of the AR is what is legally considered the gun. The upper assembly which holds the barrel and bolt is totally unregulated and may be sold to anyone. When an AR 15, M4 or M 16 is sold it usually includes the lower receiver and of course that bears a serial number, the maker’s name, etc. and of course as a gun all firearms laws must be complied with.

      80% builds sidestep all of the legal paper work as it is nothing. Just a slab of metal or plastic. Most have no stamps or other marks on them. LoL, why would it? It is just a slab of material.

      AR 15 lower receivers can be made of many materials. Plastic is not unknown. Neither is steel (makes for a heavy gun) but the most common material is aluminum. There are two types of aluminum alloys preferred for AR 15 class receivers. 6061 machined to shape, or 7075 forged to shape. I found a good source of 7075 forged receivers online ad purchased a few. Although they did come with a jig, I spent a few bucks more and purchased a more refined one from a firm called 5d tactical.

      US Federal Law allows a qualified (non-felon, US Citizen, over 21, not certified crazy, not the subject of a protective domestic abuse order, etc.) non-licensed individual to make a firearm with only one caveat. The weapon built may not be sold or given away without first obtaining a serial number for it from the Federal government (a fee payment is required). Also of course local laws may or may not prohibit the possession of a gun or a non-registered gun.

      Luckily I live in an area without any laws restricting my making a gun.

      I completed an 80% build and below is a video of highlights of the process. Elsewhere (under modren firearms) is the results of a test firing. I machined the lower receiver, added military surplus parts and also from a variety of parts suppliers assembled what I believed to be the perfect upper rifle assembly.

      I found completing an 80% receiver an educational process and think everyone should do so at least once. I have arrived at some conclusions you may or may not wish to dispute. The first is that the process is fairly easy. I moved slowly on my lower receiver so it took two hours and several cups of coffee. I don;t need as much caution now because I know the process and I think a second one would take maybe 50 minutes from start to the placing of the last pin. Second, I no longer see the need for the 80% kit beyond convenience. The jigs I have would be usable on any slab of metal with the proper dimensions. An AR15s grip attaches with a screw. Hmm, doesn’t have to. One could probably dovetail notch it in with a retaining catch, etc., etc. There are critical dimensions to memorize (the safety lever needs a 3/8″ drill hole, the trigger pin is a 5/32″ drill hole, etc., etc.) also placement angles and relationships need to determined and understood, but they can be memorized so the jig would not in a pinch really be needed.

      My grand conclusion is the very concept of controlling firearms by regulation of their sale is absurd because anyone with some scrap, the knowledge and some basic tools can make one in only a few hours. I invite your comments.

    • #796
      LittleMan
      Keymaster

      Here is 5D Tactical’s own video on using their Jig to machine out an AR 15 billet with a router.

      Here isHere is a test firing of the home built lower receiver after installing the internal parts and when mated to an upper supplied by Stag Arms.

      As you can see the home machined AR15 works perfectly. The cost of the aluminum billet was $80. The cost of a bag of mil spec parts was %60. Compare that to the cost of purchasing an AR15 lower built by someone else at your local gun store (usually upwards of $400. Note also, because you started with what is just a funny shaped block of aluminum no background check or waiting period was needed to buy the billet. They are also available in plastic should you wish to go that route.

      Yes,, you will need a router. Many home work shops already have a router for wood work. You will also need a jig. That’s additional money, but usually less than $150 and you can use it over and over if you were so inclined (or sell the jig to someone else making their own AR).Once you have a jig you can photo copy it and make a new one any time you feel like it, using the photo copy as a template.

    • #918
      LittleMan
      Keymaster

      Having already adjusted the zero of the Bushnell TRS25 sight I try the UTG 3x magnifier.

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