An AR-15 From Scratch With Billet Rifle Systems 80% Lower Receiver – Part I

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.


Machine, etch, anodize, Cerakote, assemble and shoot.

Now that we have the disclaimer out of the way! Should you desire to build your own AR-15 rifle you have several options. The first, if you have lots of time, money, and technical expertise is to buy a lower parts kit and stock, fabricate your own barrel, and mill out your own receiver. Due to the time and cost involved this would be a very long and expensive process. You could also buy a complete upper receiver assembly, lower parts kit, and stock, and contact your local gun shop to purchase a stripped lower receiver. Another alternative would be to bypass the Federal Firearms License/background check process, purchase an upper receiver assembly, lower parts kit, stock and buy an 80% lower receiver. An 80% lower receiver is an unfinished AR-15 lower receiver that requires the end user to mill out and drill the last 20% percent to make a functioning receiver that can accept a lower parts kit. The first section that the end user must mill out is the pocket that will contain the hammer, trigger, and disconnector, as well as the slot for the selector. The end user also drills out the holes for the hammer pin and the trigger pin. Having milled out the last 20% you can etch, anodize, and assemble your rifle.


80% lower compared to 100% lower. Notice the aluminum that must be milled out.

A lower receiver completed beyond 80% is considered a firearm by the BATFE, hence the name 80% lower. Given the rise in 3-D printed firearm components and “do it yourself” firearms, I was interested in the process of completing an 80% lower. As previously mentioned I wanted to complete an 80% lower with tools commonly found in hardware stores. The 80% lower that I chose to review/finish for this project was the Billet Rifle Systems 80% lower receiver.

Billet Rifle Systems, of Carson City, Nevada is a relatively new company. Started by Chris Garrison in the latter part of 2012, the company has a nice catalog of accessories and parts for the AR-15 family of rifles. At present the company’s flagship products are its AR-15 lower receivers. Billet Rifle Systems holds a Type 7 Federal Firearms License and manufactures both 80% and 100% completed lower receivers. When I queried Chris about his company’s core values, without missing a beat he responded “Customer Service and Quality Control.” Chris sent me a “blemished” 80% lower to practice on as well as one in mint condition. I really had to look close to find the “blemish.” Aside from a minor tool mark in the magwell, the lower receiver met size specifications and should serve fine as a complete functioning lower receiver. Billet Rifle Systems manufactures both 6061 and 7075 aluminum receivers as well as the corresponding jig set that is necessary to complete an 80% lower.


Billet Rifle Systems manufacture a beautiful lower receiver.

We have a lot of necessary material to cover in regard to building your own AR-15 lower, so I have broken this presentation into several articles. The first article is going to cover the tools and parts necessary to complete your lower receiver. This is a do-it-yourself type build, so I will use equipment and techniques that are logistically feasible to the general population. I will be using common tools found in most hardware stores. I will discuss tips and tricks I discovered during the builds. The second article will talk about the actual process of milling out the lower receiver and assembling one from a lower parts kit. The third article will address anything relevant and important not addressed in the previous articles, and show a complete AR-15. The overall process is time consuming but not overtly difficult.

In order to complete your build you will need the following…

Ryobi Drill Press.

Drill Press. This is a 10 inch Ryobi that has so far worked out superb. Granted a milling machine, lathe, or CNC machine would be much better: I wanted to approach this project with common tools and equipment. While working on the 6061 aluminum lower receiver I had the RPM set 3050. I have read that I may have to slow things down when I start milling out the 7075 test lower

X/Y Mill vice.

X – Y Drill press milling vise. This tool is invaluable. Notice the C – clamps that are holding the vise to the drill press table. This has become one of my favorite tools in the shop. I strongly recommend you get a vise like this should you undertake an 80% project.

Tools, bits, calipers...

Hobby vise, oil, 80% lower, Jig set, diamond files, calipers, end mills, eye protection, 5/32 drill bit and brushes for removing aluminum chips. If you cannot afford a complete end mill set all you need are 2 and 4 flute 3/8 end mills to machine out the last 20% and the slot for your selector. You will need a 5/32 drill bit to drill out the hammer pin and trigger pin holes, as well as a 4 flute 5/16 end mill, to machine out the slot for the trigger.

4 Flute and 2 Flute end mills.

4 Flute and 2 Flute 3/8 x 3/8 end mills.

Favorite tools in the shop.

You will learn to love your calipers. One can get spoiled with digital calipers!

As of writing this I have completed work on the practice lower but I have yet to assemble it. According to the blue prints I am working with, and compared against a spare lower receiver in the safe, all the measurements look good. I have learned a lot of tips and tricks that I will pass on in the next article.

Before I finish I would like to thank VaderSpade over at as well as USMCDOC14 on Youtube. Their tutorials are excellent and I learned a lot. Thank you Gentlemen!

Read Part II here. 

Thomas Gomez

Thomas Gomez currently resides in the mountains of central New Mexico. He has an M.B.A, an Ar-15/M16/M4 armorer certification from Specialized Armament Warehouse as well as a Glock armorer certification. Aside from writing for The Firearm Blog he works as a Clinical Analyst for a large Hospital. He spends his free time farming, ranching, hiking, fly-fishing and hunting in the beautiful forests and prairies of New Mexico. He can be reached at


  • noob

    Nice! That will be a proud addition to your collection. Will you press your own AK also?

    • Right now we only have this project planned.

    • Thomas Gomez

      Hey There noob! At the moment I am pretty consumed with this project. Who knows what will happen in future! Good to see you in the comments!

  • gunslinger

    Can you give a cost estimate to purchase those tools? I bet most people would have some of those components, but not all.

    i’m just curious because if a SLR is say 150-250, and a 80% is only 70, it seems good, but ifyou have to drop another 500 for the tools, it’s not worth it, unless you plan on doing several.


    • The point is to make firearms that are unregistered not to save costs.

      • gunslinger

        I would classify people who do this into 3 groups..

        1) will pay anything for an “unregistered” firearm. they’ll pay any price
        2) “builders/hobbiest” those who like to tinker around and take on DIY projects for the sense of accomplishment. but they have limits to what they will spend this is their hobby. they may already have a press/mill with a vise, but wonder what additioal tools they need.
        3) someone who wants to piece together the pieces of an AR for as little as they can. they figure in the cost of parts, as well as any tools needed.
        so as i stated before, if you are going to review this, could you get a cost estimate of what the parts are? thomas said he wanted to see if this could be done with tools bought out of a hardware store, so that right there tells me there is a cost factor in this review.

        • tincankilla

          right on target – the only reason i’m interested is #3. maybe a bit of #2. bottom line is that if i can’t buy or build an AR at a reasonable price, I’m going to spend the money on the guns i already have – shooting, tuning, etc. there are better places for my cash than some other guy’s fishing boat.

          • Thomas Gomez

            “tincankilla” Love that name!

        • junyo

          I’m in group 1, after the last battle. Formerly a member of group 2. Unless an AWB passes, or you own a machine shop/CNC mill, it will almost always be cheaper to buy a complete lower. Unless you only need a couple of drill bits, there’s not way your costs on the first one will be lower than some shop can crank them out for. And what really drives up the real world cost is time. If you have zero interest in learning the process, you can repay any price delta with a few hours of overtime versus messing around in the garage.

          • Thomas Gomez

            You are 100% correct! Thanks for the comment!

        • Thomas Gomez

          It’s nice to be self sufficient when it comes to firearms.

        • Thomas Gomez

          Right on Gunslinger. It would be terribly unprofessional if I used high end equipment generally not available to the public. I definitely approached this is something that would be feasible to most handy men..and women. I can tell you that Harbor Freight has most of the tools you need to knock out this build. They even have a mini lathe!!

      • You got the point! That and you learn and that’s a good thing!

      • Thomas Gomez

        Autonomy. Freedom…being self sufficient. It’s incredible what you learn when you build your own hardware.

    • Thomas Gomez

      Gunslinger. That vice was about 60$ at Harbor freight. The press was around 150$. The end mill kit was about 80$ at Harbor freight. I have used these tools for other gun related projects. I had to mill the scope base on my brothers rifle due to the fact that the magnification ring was making contact with the base. Hope this finds you well!

  • While I get the DIY thing, perhaps a more efficient and cheaper way to finish an 80% lower is take it to one of many places that are set up to mill the last 20%. You rent their machine for $30 or so. Clamp the lower into the already set up CNC machine, press the button and you’re good to go. Still DIY but on their machine.

    • In cali all the places that allowed use of their machines were warned by the ATF it is not allowed. It has to be your machines you can not rent them.

      • gunslinger

        got documentation on that?

        • No my friend lives out in cali just made a couple ak47 at solar tactical i believe. they would have groups come in people would use their machines and build their lowers and guns. AFT contacted that company along with others in the area forcing them to stop doing what they were doing. They basically said it is only legal for people to use their own equipment what they are doing they consider renting machine time which is not allowed to build their weapons with. I think its illegal for the shop not the individual.

        • If you do it yourself you’ll be ok but once you have a company involved it becomes a manufactured lower not a DIY project.

          That’s from the local ATF office.

          • gunslinger

            well what’s the difference between “renting” time at bob’s mill shop (renting time on equipment at bob’s shop floor), and renting equipment from “bob’s rental equipment” (take said equipment from bob’s shop to an offsite location) and buying from “bob’s hardware store” or going to your buddy bob’s house and using his equipment in his basement?

          • I have no idea at all that makes sense but hey it’s the ATF!

          • I built two and rented a CNC machine. The whole ATF thing was a rumer started becasue one shop got a ATF letter becasue they were making the 80 and also finishing the 80. You can purchase at one shop and finish at another doing a machine rental. Here in cali its huge.

      • Rod

        IT would be the CA DOJ, not the ATF. The ATF is Federal.

      • Shawn

        So you’re telling me that I can’t rent a machine from someone and do it myself legally? That makes zero sense.

        • cw

          Because all other gun laws make lots of sense, just not this one.

      • That was a rumer one place was warned that they can not make and finish at the same shop.

    • GlockIt

      Any idea where I could do this in so cal?

      • Dan Donovan KE Arms

        yes, I have a great place for people in so cal. send my an email-

    • Gary Patterson

      What is difference with these billet lowers and the forged ones bought from and aresarmor.

    • Gary Patterson

      Very simple process with a drill press and nice vice and a few drill bits, Bought an 80% lower from and a drill/mill jig and finished part in an hour or so, worked fine, no problems.

  • zeos

    $170 for an unfinished lower vs. $110 normal lower + $30 transfer fee, I’ll stick with the normal route.

    • Mystick

      Where are you finding a $110 in-stock 100% lower nowadays?

      • Robert S

        Palmetto State Armory has them in stock every few days. Just check every now and then and you’ll see them

    • User

      $110 for a lower? … In stock? Link please.

      Also, I don’t know of any shops in CA that have fees lower than $70 for transfer. =(

    • junyo

      Just got 6061 80 percenters off a startup machine shop for $65. Pays to look around.

    • Gary Patterson

      bought forged lowers from for 105.00 and they are in stock.

  • Karl Erich Martell

    Nice article, vecino.

    • Thomas Gomez

      Gracias amigo! What part of New Mexico do you call home?

  • Nick (CNC Machinist)

    This is absoulty HORRIBLY advice and practice to use a drill press as a milling maching. Do at your own parrel however I warn anyone that attemts this, you will destroy the press as it is not made for milling operations and you will not get anywhere close to tolerance; turning your 80% into a paper weight. If the drill press is your only option, get a drill jig. Otherwise use an actuall milling machine.

    • gunslinger

      saw this advise on other AR15 forums, but had no real answer as to why.

      what makes the mill suited for this vs drilling. I’m not a machinist, and to me it looks like you have a bit that is removing metal. so what gives?

      • David Hinerman

        A drill press is designed to only withstand force applied straight down. A mill is designed to withstand the lateral force of moving sideways through the material. Putting lateral force on a drill press will bend something.

      • thrux

        radial forces on the head. a mill is built to tolerate and resist those forces. a drill press is not

        • gunslinger

          so during the process you’d keep the drill head down and move the part? Wouldn’t this be “solved” by just doing a bunch of drill through

          • Thomas Gomez

            Hello gunslinger. You are correct sir. I will make it clear in the second article that I only advise milling along the Z plane and not to move X or Y while the mill is making contact with the metal.

      • Mystick

        Bearings… Drill presses don’t have the same bearings that a mill does around it’s axis of rotation.

    • Thomas Gomez

      Hello Nick. You are absolutely correct. One thing I will make clear in the next article is that once the mill end is sunk and making contact with the aluminum it would be ill advised to move the mill along the X or Y planes. I completely mill only along the Z plane. Press into the metal and mill what you want gone….raise the mill so its no longer making contact with metal….move the vice….press down….repeat, repeat, repeat. Thank you for your insight! Hope this finds you well!

    • Zeus

      I hope your machinist skills are better than your spelling. Wow.

  • somedumboathkeeper

    I don’t see anywhere in the law where destroying the unmarked receiver is required nor having to transfer it via a FFL. You may only manufacture if you lack the intent to sell it. You can develop the intent to sell it at some point in the future and you can transfer it without a serial number. You may not get a FFL willing, but you can do an in-state transfer and it would be perfectly legal as long as you didn’t intend to sell it when you made it. You could also make as many as you wanted as gifts. As for the comment about ATF saying you can’t complete a lower on someone elses machine, that rings of complete idiocy. You are the manufacturer if you are working the machine, which includes pushing the ‘start’ button on a CNC mill. It’s just ATF scaring people with no legal basis.

    • Thomas Gomez

      A lot of that depends on a judges interpretation. Thanks for the comment!! Hope this finds you well!

    • So then, is the guy who runs the machining center at Ruger that cranks out the AR-15 lower receivers “the manufacturer” or is it Ruger, the holder of the FFL? It’s Ruger, of course. So if you are using the machine to manufacture firearms at a place that is in the business of manufacturing (even if they do not manufacture firearms, or are even licensed for it) then that would make THEM the manufacturer, not you. I think the ATF’s interpretation in this particular case is actually spot on.

      • t-dahlgren

        If that were true the ATF would have already charged the companies for the ‘illegal activity’ they instead chose to threaten.

        The machine shops are not engaged in the business of manufacturing firearms, for sale or otherwise.

        They are in the business of renting shop equipment and space to people who might then use that equipment to make their own personal use firearms. Or those people might use the equipment to make ashtrays, paperweights, or anything else.

        It is the renter who chooses how to employ the equipment therefore they are not an agent of the shop (unlike the employees at Ruger) so the shop is not directly responsible for their choices.

      • Ok

        One problem with your statement ruger don’t make thier ar15 receivers .

  • how about making full auto lower receirver?

    • Thomas Gomez

      Hey Jack. That would require a lot more paperwork with the BATFE. Hope this finds you well!

    • Mystick

      The article covers that… you need to get the paperwork for it…. and the tax stamp.

  • Matt Porter

    Man I enjoyed this article. I would recommend your spindle speed closer to 1600. I am a rookie machinist so take what I say as a grain of salt. It is possible to mill X and Y planes via a drill press but your feed speed has to be SLOOOOW. With a 9/64 carbide end mill I was able to mill some S7 tool steel the other night. I don’t recommend it for someone who hasn’t milled before.

    GREAT article. Can’t wait for the others in the series.

    • Jack

      It is possible but will damage your machine, cutting tool, and give you irregualr cutting patterns on your work. Even more so if you attempt to climb mill. If you want to get into real milling but have a tight budget, I would recomend getting a hobby machine. The Siege x2 and the mini mill the Harbor Frieght carries are the same machine and will do a proper job milling out AR lowers and other milling task. Better yet, you can easily convert it to CNC if you wanted.

  • Kevin M.

    looking forward to part 2.

  • what type of MILLING machine would be recommended. Might as well go big….

    • Talked to the guys over at and most of the people buying these are completing on drill presses, but a small mill with x/y vise is recommended

  • Eugene Berman

    Any update? Can’t wait for the part II! This is exactly my scenario, I have an 80% lower and exactly the same drill press.

  • Max

    Are we going to see the rest of this series any time soon? I have an 80% lower and have been researching the finishing and want to see great write ups like this go through the whole process.

  • usmcdoc14

    Glad I could help you out with my video. If you have any requests please ask!

  • Chris

    free pmag with purchase over Memorial Day with coupon code: pmag at

  • Zeke Freebier

    Definitely ready for the next installment!

  • orsillac

    As we have learned over the past few weeks, the US Government can and has been tracking our phone calls, e mails, on line searches and credit card purchases. So the question is how can we purchase on line and keep it private? Can we purchase a prepaid debit card with cash and use it to make on line purchases? I have heard that some on line retailers require that the card be registered and that to do so you must give your name and address to the card provider and use the same name and address as the billing address when making an on line purchase. Can one make up a name and address and use that same made up name and address as a billing name and address, but use your real name and address for shipping? And if you do, is it private? As far as private e mail and on line searching is concerned have a look at ixquick, firstpage, and hushmail. What do you use for surfing the web and e mail? Do you feel they are private?

  • SrGunney

    You all were talking about Renting a CNC Machine that is pre set up so that all you need to do is hit the Start Button… May I point out to some of you that the Set Up of these machines is part of the manufacturing process… And that if an Employee of said Rental Shop goes in and Pre configures or programs the Milling machine to do the tasks necessary.. which is not at all just pushing a single button… then the rental shop would indeed be involved in the manufacturing process. I absolutely hate to agree with the ATF on this but, but it sounds to me like they are Spot On. Now.. If you rented a Ryobi Drill Press… or even a ^Handy AR-15 Jig^ and went home with it… it would be another matter… Or if you had to totaly set up the milling machine for the job yourself… it might would fly. But not with them doing the Programming and set up for your project. OK.. Just my oppinion.. watch your Backs as you all know Big Brother is Watching….

  • Ringo Lapua

    Ask anybody who owns or sell guns if they are against “GUN CONTROL” and you will always hear a big YES. With that said, all of the same people ACCEPT THE ATF with their silly abusive and nonsensical rules as gospel. WHY? because they will confiscate our weapons, fine us or put us in jail? Sure, a good reason to abide by, but it does not mean that we cannot BAND TOGETHER to BAN THE ATF’s involvement with handguns, rifles and accessories. While common sense dictates that major weapons of war, missiles, grenades, rockets, etc. should be kept out of the public hands, gun laws applied to pistols, rifles & accessories (ex. AR-15’s, short barreled rifles and suppressors) should be immediately ELIMINATED. Write your Senator and Congressman and GET THE BALL ROLLING. STOP THIS GOVERNMENT GUN CONTROL NOW.