Machining an AR-15 Forged Lower Receiver From A Forging

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Being from the industry, it was surprising to see a video pop out on the physical and full machining of an AR-15 lower receiver. The “secrets” to machining the lower correctly and with the minimum amount of machine time are closely guarded secrets by most of the industry. Even a reduction of one minute can mean large swings in margin for a manufacturer. Efficiency is key.

Bucking the trend is Palmetto State Defense, not to be confused with Palmetto State Armory. Instead, PSD has opted to showcase the full cycle in all its glory, including fixturing, cut paths, etc. Surprisingly, Palmetto State Defense opts to broach the magazine well corners directly in their vertical machine (most companies broach separately).

In fact, the fifteen minutes needed to take a lower to 80% is mesmerizing. Its incredible for one to understand the complexity of the cuts and the number of tools needed to complete a “simple” lower receiver from a forging. Of course, billet would take extra time as it would require machining the exterior of the part.

For those interested in “how its done” the video is posted below from the machine spindle’s perspective.¬†Finishing the lower would only be a few more minutes on top of the machining show.

 



Nathan S.

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

Nathan can be reached at Nathan.S@TheFirearmBlog.com

The above post is my opinion and does not reflect the views of any company or organization.


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  • VanDiemensLand

    Reminds me of watching Diresta…

  • jimmie

    I have a few lowers from them, as good as any others I’ve bought and local to me.

    • marine6680

      I bought one from them too… The local store that had them closed up. I think they were the direct link to the guys making them.

      The one I have has the older logo.

      It was a bit tight in the bolt stop area, but otherwise well made and finished.

      I was using it for a dedicated 22 build, so no worries about the bolt stop being a bit stiff to operate.

  • datimes

    The video lacks the action of an old Clint Eastwood movie but was interesting and informative.

  • DIR911911 .

    ” AR-15 Forged Lower Receiver From A Forging” . . . because forged receiver is forged

    • iksnilol

      Can’t you make a forged receiver from something else tho ?

      Does it really have to be from a forging?

      • randomswede

        On the off chance you aren’t trolling; No a forging is metallurgically different from a uniform chunk of metal.
        Mostly the AR-15 was designed around forgings because it’s cheaper but I understand that they are stronger by weight compared to those milled from uniform stock, what gun guys know as billet.

        Here’s a picture illustrating how they are different, I think you need an electron microscope to see it though.
        https://uploads.disquscdn.com/images/b376e7d5b25900742ce779f641086ca57c3f9f6f287fd79178f9ba8b42b8ec87.jpg

        • FarmerB

          Great thanks. I never really thought about (understood?) the difference between casting and forging.

          • randomswede

            They tend to look similar as both processes usually leaves flash where the excess material “escapes” the casting mold or the forging dies.
            Castings are cheap and great for many things but they tend to break where forgings bend.

  • Lefty Bookwurm

    Speaking as a CNC Machinist it doesnt give away as much as you think it does. you machine it with a cnc mill because you HAVE to use a mill, CNC because it is fastest, most economical, and because you can have one guy running at least 3 of them. the fixturing is predictable. you need access to the top, left, right sides to true it up. then stick it in the rotational axis to do everything else. they could even post the code that the machine is running. that wouldnt give anything away at all because if you tried to use it, you’d crash the machine if youre lucky.

    • randomswede

      I was surprised at how, conventional or perhaps generic is a better word, the fixturing was, I would have assumed they’d do everything they can to get the refixturing time down.
      I’m not a machinist myself but I watch very many on youtube so…

      Am I right in assuming that the code is quite fancy with that many touch offs or is it just a stack of simple programmes?

  • 11b

    I’ve long thought about using something like an X-Carve to make AR lowers. Wood working tools can effectively machine aluminum, although it’s slow, but I’m not sure a CAD file is publicly available for something like that…?

    • randomswede

      There’s the “Ghost Gunner”, it starts from 80% lowers and takes them to 100%
      I think it can be done with an X-Carve, but I also think you’d be better off with a smaller more rigid machine, downside being cost upside being you could probably start from a forging or a piece of billet.

      There’s a few sources for AR-15 CAD files grabcad is good place to start though, there of course is no such thing as an official CAD file.

  • Christian Hedegaard-Schou

    Didn’t even know you could broach on a CNC machining center like that. Seemed like a VERY slow way of doing it though.

    • GaryOlson

      Sure, it’s slower. But like any manufacturing process, you evaluate cost of operations vs the cost of building and operating a completely second process. In small runs, I’ve broached on a CNC because it eliminates the secondary setup. Uniformity in final product was less; but overall turnaround time was faster.

      • randomswede

        Seams to me it stacks up quite well to EDM, at least considering setup times.

        I’ve also seen beautiful broaches that starts from a milled slot to a Mil.Spec. magwell in one step, that takes an impressive press though.

  • Black Dots

    Anyone have a link to a lower being forged? I’ve never seen that.

  • Chris Mooney

    Money shot at 2:57

  • Martin M

    Much more impressive than the ‘birth of a Glock’ frame.

  • jerry young

    As nice as this is to watch not many people have the money or knowledge to do this but it is cool, I just do the 80% lowers, I did my first using a drill press then bought a bench top manual milling machine, I taught myself using what info I could find, it’s not that hard!

  • Stevie P

    I can smell the coolant now! Lol, Haas mini mills are fun to use and play with, one of the easier CNCs to operate.