Finishing 80% Lower Receivers

Hi All,

I just posted a YouTube video showing the use of a Shapeoko to finish an 80% lower receiver using prototype tooling from CM-Tactical. I will post back in this thread with pricing and availability details once I have them for anyone interested.

This is a demonstration video only. I will try to post an instructional video as I can put one together, but I strongly suggest you familiarize yourself with the Shapeoko videos by Winston Moy for working with aluminum. The Shapeoko cuts aluminum well, but there are many things to keep track of with aluminum that aren’t as critical when cutting wood. Winston provides good tutorials for cutting aluminum. I recommend trying something simpler than an80% receiver for your first aluminum project.



I’ll be the bad guy again and respectfully remind that the forum terms of use has a “no commercial activity” rule (there is some tolerance but we need to keep it fair for people who we previously told the same).

A further complication here is that this is an international forum, Carbide 3D doesn’t have an FFL, and we haven’t paid our lawyer to navigate the intricacies of ITAR.

It’s okay for customers to discuss firearms projects, but we can’t directly assist (not having an FFL), nor do I believe that we can host files directly related to firearms manufacture (because of ITAR).

That said, thank you for posting that — great to see a Stepoko in the wild!

Hi Will,
I’m happy to abide by C3D policies, but didn’t find any references to firearms prohibitions mentioned. I concede that I may have not looked in the correct place!

As to ITAR, these weapons are not classified as military (AR15 vs M16 or M4) and are therefore not even remotely in the scope of ITAR. Forums all over the internet discuss the finishing of 80% receivers and have been found to be acceptable under first amendment freedom of speech guarantees. Further, former President Trump passed ITAR reforms in 2020 allowing residents to freely publish technical arms information, son there would be no ITAR restrictions in any case.

That said, I completely respect any position C3D takes on this. I have so far had a good relationship with you guys (even with the Stepoko :wink:) and wish to maintain it. I will not publish the follow-on how-to if that will keep me in C3D’s good graces.



Hi Julien,

Apologies! I will forego mentioning when these become available per your comments. If I could figure out how to edit my post I would remove references to the future availability, etc.



It is okay for you to post a complete walkthrough here, it can be step-by-step and even include screen grabs so that a person could make their own version of the files — the problem is there isn’t any case law on this which indemnifies folks from hosting files for international distribution, which is why that is the (only) limit I think needs to be in place, since arguably:

1st Amendment + 2nd Amendment == the Right to 3D print and Bear Arms

To expand on the above, many countries classify firearms as military based on caliber, so a weapon designed for 5.56mm NATO would be a military one, and of course with source files, most weapon designs could be reworked to accommodate other calibers which would be viewed as military such as 9mm Parabellum.

Lastly, it’s okay for folks to discuss that they make products for sale, and have them for sale — the only thing we ask is no direct links to sales/product pages or commercial sites by the folks running them — and it’s okay for other folks to post links to pages which they have no direct affiliation beyond customer.

I hope that makes our stance clear, and provides a reasonable context, but also sufficient freedom for discussion and instruction.

Naturally all of the above is subject to modification and adjustment by the folks who actually run things.


I believe, not 100%, that you can discuss how to finish 80% lowers, but sharing the exact gcode file is restricted. That being said I’m not sure why someone wouldn’t want to make their own toolpaths for something like this.
In January I finished up painting 2 lowers I had completed on my shapeoko. Honestly the hardest part of all of it is figuring out the work holding as the toolpaths are relatively simple pockets.

THE MAN HAS NOT SHOWN A FIREARM. Good grief, its a chunk of aluminum no different than one of those much more dangerous intake manifold vehicles that Vince produces. :roll_eyes:


I like seeing the skills that everyone on this forum demonstrates everyday and am anxiously awaiting my NOMAD3, designing model airplane parts in Fusion in the meantime. I’m not in any way trying to propagate a 2nd amendment discussion here. I just thought that this article might be found interesting to the readers here regarding legal precedent that has been proven that AR lower receivers are not considered a firearm.

Are Lowers a Firearm?

You’re right, and for most normal folks anything firearm related is part of 2A and not a big deal. But, unfortunately, in today’s politically correct, “progressive” world, just using the “G” word is offensive and means you are a right wing extremist and are about to shoot up anything and everything that moves!


Legalities and all aside, I see it as “when you are in someone else’s house, you go by their rules”…
they ask you to not post it here, you don’t post it here… not so difficult.


Thanks Will,

Well worded and clear. I appreciate it!


Hi Sarge,

I agree about wanting to create your own tool paths. Especially when cutting aluminum it is good to know the peculiarities of your particular machine when setting feeds and speeds. I believe that the folks at CM-Tactical plan to provide the model for the fire control group hole with the correct zero so that people can build their own tool path.

I worked out the tool path I used in this video with CM-Tactical and relied heavily on adaptive clearing and pretty high feed rates. I probably wouldn’t have been comfortable with that except I have already cut a lot of aluminum on my machine. Some machines will be tighter or looser than mine and will be able to cut faster and slower than I was able to.

As to workpiece holding, that is the thing I like about this tooling! It makes locating the receiver and setting the zero simple, easy, and repeatable. I have previously cut these out using a vise mounted on a dropped down table in a cut-out from my work surface. Although I could make that work, this is both much easier and more secure/stable than that solution (imho).

Thanks for your thoughts,


I made a custom clamshell vise that bolted together to hold the lowers, which worked great, but making sure it was perfectly square to the machine is what took the most time for setup. Or maybe it was just me second guessing myself.

I also used adaptive toolpaths to do the majority of the work then a couple contour finishing paths. Apart from the milling of my custom safety markers it was all cut with the 1/4 single flute 278z. It had just barely enough reach.

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I have gone through and deleted/hidden some replies which were not as nicely on topic as we would prefer.

Hopefully I’ve done this in an equitable fashion and everyone can accept that the remaining posts add to a discussion, and that the removed posts did not contribute to the friendly and welcoming atmosphere we would prefer to maintain here.


Im interested. Thought about using our XL to complete a poly 80% I have kicking around, which would be a no brainer (although I gotta check the material, glass fill would be hard on bits). Didnt think I had enough room with the Z, but guess I should look again.

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You’re on the right track finding out the material. PEEK and glass/carbon are hard on endmills. It might also take a dedicated endmill for composites, or an o-flute for plastic.

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There is enough z (as seen in the video), but the table clearance is an issue. CM-Tactical solves this by hanging the fixture off the end of the machine. I’ve also seen people do this to get extra depth for cutting finger joints or dovetails on drawer sides, so it seems to be a common feature of these machines that folks are exploiting for a number of reasons.


Going to put in my two cents here.

There is naturally a lot of overlap in men, machines, trucks, guns… the whole lot. No argument from me! I am a veteran, and I carried these things (and other stuff much bigger) around Iraq and Afghanistan, and slept with them and fired them and I don’t think the AR is an especially good mechanism. I think looks, and maybe the military association attract young men to them. The events of the last year or so don’t exactly help their reputation by association, either.

They were originally designed prior to the widespread adoption of CNC, so they naturally lend themselves to tinkering in the hope shop, and maybe that partially explains the 80% phenomenon. You should probably temper your expectations that you can start a business finish machining them, though, since that exposes you to a lot of liability, and if everybody else can also do it in their own home shop how much value are you actually offering?

I remember reading about a guy selling a drop-in sear he 3D printed at home, describing it as a coat hook on Etsy. Didn’t he go to jail? Seems risky to me.

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I don’t think anyone is daft enough to try and finish these and sell them as a business. That would require an FFL and so much paperwork/liability. Making them for ones self is the only option if you don’t want to be a felon.

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