Weldable AR15 Receivers From The Flat Spot

Beyond legos for gun nerds comes this soon-to-be-AR15-lower (aka package of raw metal) that can be transformed with skill and welding. Designed and machined by The Flat Spot, this assortment of metal is what I have dubbed a 25% lower receiver. Whereas 80% lower kits only require a drill press and finishing, this flat set requires welding and tapping of the receiver extension hole.

Practical in the days where complete lowers can be had for $30? Probably not. However this kit looks like a lot of fun for a dedicated builder. Sure, it will end up heavy, less polished and less than milspec, but you were the one who actually brought it to life. And government, serial numbers, NICS checks, Molon Labe, yada-yada-yada stuff too.

The Flat Spot



The Flat Spot AR-15 RECEIVER FLAT – WELDABLE- $28.99

Now with NEW & IMPROVED SAFETY DETENTE PIECE (NOTE: This piece was not available on the earlier version of the AR flat and because of that it was difficult to drill the safety lever detent hole due to lack of material. Now it is included in the AR flat kit! Good news! If you have built one of the older AR flat receivers you can purchase this piece and simply add it to your receiver. Here is the link to purchase just the safety detente piece to upgrade your older receiver –

Please note – these are for builders and still require some work IN ADDITION TO WELDING such as tapping of the buffer tube hole (many builders choose to simply weld a castle nut on the rear of the buffer tower instead of tapping – We offer castle nuts here – http://www.theflatspot.net/ar-15–ar-10-castle-nut-for-buffer-tube.html), drilling détente holes, drilling bolt release pivot pin holes and some fitting. Note – tap and drill holes prior to assembly. Deburr the tab from all parts to insure proper fit during assembly. Please see the cad drawing files below for assembly instructions.


LE – Science – OSINT.
On a mission to make all of my guns as quiet as possible.
Twitter: @gunboxready
Instagram: @tfb_pete


  • Giolli Joker


    • Twilight sparkle

      Mild steel iirc
      These things have been out for many years, arfcom used to do threads on them fairly regular

      • Jim_Macklin

        Just what the market needs, a 10 pound 5.56×45 plinker

  • Anonymoose
    • Noishkel

      Interesting. What is that exactly? Looks a bit like it was stamped out of sheet metal.

      • cowboybob

        It’s a WWII-era stamped 1911 prototype made by General Motor’s guide lamp division, The same guys that made the M3 submachine gun and the FP-45 “liberator”. This 1911-based pistol worked okay, but it was big, awkward, and very heavy so only a few prototypes were made.

        In the early 30s Springfield armory experimented with making 1911s with cast slides and frames made of Bronze alloy. They worked well too, but for reasons I don’t know they never moved beyond the experimental stage.

        • Twilight sparkle

          Probably because of the price of bronze vs steel as well as the fact that bronze wouldn’t hold up as well over time.
          England tried something similar in the sten during wwii where they were making bolts out of cast bronze so that they could be produced faster but the trade off was a much higher cost.

      • Anonymoose

        It was a postwar experiment to produce M1911s out of stamped sheet metal. http://www.thefirearmblog.com/blog/2013/01/02/the-mystery-of-the-stamped-steel-1911/


        is it the General Motors effort to produce a stamped sheet steel .45 ACP pistol for emergency manufacturing….possibly to ” drop behind the lines ” to ” arm insurgents against USA enemies ?

        believe a 9mm type was also considered….

    • Gary Kirk

      Hey look, it’s the Taurus remake of a high point..

      • Stephen Paraski

        way better than a blow back high point.

  • Sam Damiano

    Not a bad price. I’d do one for fun.

  • Some Rabbit

    I’m waiting for Henry Arms to make a polished brass lower.

  • Devil_Doc

    Détente? Lol…

    • mazkact

      I caught that as well, If Pat gave you a R and a U and you’d almost have the Filipino president.

    • Brian Menin

      I don’t think they know what that word means.

  • Phillip Cooper

    No thank you!

    • felix

      It gon’ blow up

      • Wow!

        I have one, it isn’t going to blow up (that isn’t how lowers work). It is heavy though.

  • Noishkel

    Well personally I was more interested in the ‘bolt together’ projects. But this is still damn cool. |3

    • noob

      Is there an ar-18 kit like this?

    • Wow!

      Google online, there is a pdf of a lower made from aluminum pieces held together with machine bolts.

  • Brett baker

    Why not just sell a tdp for $3.95 and be more untraceable?

  • winterhorse

    I did the 80% thing a while back. Still shoots fine, but could have bought 2 nice completed lowers for the money.

    • This is what I’m running into, I want to support the 80% market & companies. But I’m on a seriously tight budget.

      Then again I might be moving back to the People’s Republic of Kalifornia in a year or two and I want them out of my private life.

    • Wow!

      Doing 80% is a whole lot cheaper when you don’t rely on buying the tool guides and have a welder, lathe, and mill. It may cost a bit, but you can get a mini version of each for a grand total under a DD rifle. Plus when you have the real tools you can start building real guns like Stens, Uzis, Macs, AK, MP5s, G3s, Belt feds etc. Not to mention the scratch builds like Bill Holmes. It totally opens your world and you can crank out a good complete weapon for usually less than $90

  • Gary Kirk

    Does this mean that we can finally use our AK tool for our AR builds??

  • iowaclass

    What about crazy-glue?

  • nadnerbus

    Just give me a couple tubes of JB Weld, and I’ll give you an AR. And possibly shrapnel wounds.

    • Rob

      Instead of tapping the buffer tube just jb weld it in place. & maybe add setscrews.

  • DW

    How about milled aluminum ak receiver for a change

    • Wow!

      Why would you ever want a milled ak receiver aside from an original collector item? They are heavy, expensive, time consuming to make, and supposedly are not very reliable compared to sheet metal receivers.

  • jerry young

    I’ve done the 80% lowers in my drill press and even bought a milling machine to improve my work now I want to try this, not sure what kind of welder you need but I have a variety of them from stick to tig from gas to mig and even spot welders, so what’s next a sheet of steel with templates to cut out the pieces yourself? I have a plasma cutter too! Will the next kit to come out be raw iron and forge, you’ll get a hammer and instructions how to forge your own AR sounds like fun to me! all kidding aside I do want to try this.

  • mazkact

    Anderson lowers for the win. Ya I know , I know da gubmint will know.

  • Paveway

    Industrial Strength Glue?

  • noob

    Thanks! I’ll have a look through their catalog

  • ironked

    Might just be the time to finally buy that sub-$100 Harbor Freight wire fed welder.

    • Wow!

      Just DO IT!~

    • BraveNewWhirled

      You think it would last long enough to finish the project?

  • Bradley

    These are steel

    • Matt Taylor

      You could use whatever metal you’d like. I’m thinking of getting the plans just to build me a nonfiring brass model for a steampunk looking prop gun..

      As for these for an actual AR? Interesting idea… not so interesting execution.

      • Bradley

        Yes you could, but the onesin the article they sell are steel…

  • Amplified Heat

    What fool would pay to have one of these built? Missing the point entirely.

  • Matt

    That looks like a huge pain in the ass. compared to an 80%.