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Interesting milestone in open-source 3D printing over at Thingiverse: User crank has published a freely-downloadable magazine for the ubiquitous AR-15 rifle. As downloaded, crank’s magazine only holds five rounds, but a person with basic 3D modelling skills could modify it with little difficulty to produce a “high-capacity” magazine. I’m not sure what the current state of law on magazine size limits is, but prior to the sunset of the Federal Assault Weapons Ban (Wikipedia) in 2004, manufacture of an AR-15 magazine with a capacity of more than 10 rounds was an offense.

Crank reports that the magazine—which consists of a printable body, follower, spring, and baseplate—is fully functional, at least for a few rounds:

I have used this magazine, no jams or feed problems….. YET. It works, but be reminded it is only a printed ABS magazine. If you end up using a printed ABS mag spring be prepared for stress relaxation of the polymer over time, especailly [sic] if it is kept loaded over a long period of time.

As published and as printed by crank himself, I should emphasize, this magazine is (as I understand it) completely legal, and would’ve been legal even before the ban expired. But the file raises some interesting questions.

In response, user KingLudd has uploaded a printable lower receiver for an AR-15. If you own an AR-15 rifle and want to buy replacement parts for it, you can easily buy—in person or through the mail—every part of the gun except the lower receiver, without any kind of legal controls on, or records of, the sale. So the manufacture of a lower receiver is tantamount to the manufacture of a functioning, extralegal, unregistered AR-15. Unlike crank, KingLudd has posted no photographs of the printed part or otherwise done anything to suggest that he has actually printed and/or tested it, because actually doing so—absent a federal license to manufacture a working AR-15—is unambiguously illegal.

Update: The stricken sentence is false. At the federal level, at least, licenses are required only to manufacture AR-15 lower receivers for sale. Thanks to our commenters for catching and correcting the error, which was based on my mistaken belief that an AR-15 is a Title II firearm and hence subject to the provisions of the National Firearms Act. Apologies for the misinformation.

Sean Michael Ragan

I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I write for MAKE, serve as Technical Editor for MAKE magazine, and develop original DIY content for Make: Projects.


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Comments

  1. Jason Winningham says:

    Manufacturing a lower for your own use is perfectly legal, unless you live somewhere like the People’s Republic of California.  I’m sure the bureaucrats at ATF have specific guidelines on the number of receivers per unit time you can make for yourself before they don’t consider it “personal use”, but making one is no problem in most parts of the US.

    Check facts before you make statements like “unambiguously illegal”, since it’s dead wrong in most of the US.

    1. Wes Nott says:

      No Jason, it’s legal to manufacture an AR-15 lower even in California. I completed an 80% lower receiver using my Drill Press and Dremel Tool.

    2. Wes Nott says:

      No Jason, it’s legal to manufacture an AR-15 lower even in California. I completed an 80% lower receiver using my Drill Press and Dremel Tool.

    3. Wes Nott says:

      No Jason, it’s legal to manufacture an AR-15 lower even in California. I completed an 80% lower receiver using my Drill Press and Dremel Tool.

  2. Jason Winningham says:

    Manufacturing a lower for your own use is perfectly legal, unless you live somewhere like the People’s Republic of California.  I’m sure the bureaucrats at ATF have specific guidelines on the number of receivers per unit time you can make for yourself before they don’t consider it “personal use”, but making one is no problem in most parts of the US.

    Check facts before you make statements like “unambiguously illegal”, since it’s dead wrong in most of the US.

  3. Jason Winningham says:

    Manufacturing a lower for your own use is perfectly legal, unless you live somewhere like the People’s Republic of California.  I’m sure the bureaucrats at ATF have specific guidelines on the number of receivers per unit time you can make for yourself before they don’t consider it “personal use”, but making one is no problem in most parts of the US.

    Check facts before you make statements like “unambiguously illegal”, since it’s dead wrong in most of the US.

  4. Michael Curran says:

    I’d double check the law, arresting someone building a legal gun for personal use would probably run afoul of the 2nd amendment in a hurry. All federal permits on the topic involve the manufacture or importation and sale of said weapons.  

  5. Michael Curran says:

    I’d double check the law, arresting someone building a legal gun for personal use would probably run afoul of the 2nd amendment in a hurry. All federal permits on the topic involve the manufacture or importation and sale of said weapons.  

  6. Michael Curran says:

    I’d double check the law, arresting someone building a legal gun for personal use would probably run afoul of the 2nd amendment in a hurry. All federal permits on the topic involve the manufacture or importation and sale of said weapons.  

  7. Tom Cook says:

    Not so sure about it being illegal to make, probably only illegal to make and sell. The other discussions I have seen it seems that as long as you make less than 5 a year and don’t sell them you are fine.

  8. Matt says:

    Your claim that printing an AR receiver “absent a federal license … is unambiguously illegal” in unambiguously false. Title 18 of the US Code states that an unlicensed manufacturer may make a receiver but may not sell it without a license. Many gun owners in the United States, myself among them, have chosen this method to obtain a firearm, with AR-15 and AK-47 variants being the most popular (they’re the easiest to make).

    A simple search for, say, “homebuilt AR receiver” would have turned up dozens of useful links for building a receiver from scratch, with photos from those who have done it, all posted without fear of federal prosecution.

    As far as the magazine issue goes, there is no federal ban on magazines, either by size, capacity, manufacturer, manufacture date, or intended firearm. State laws vary, with places like Virginia and Arizona being sensible, no restriction jurisdictions, while California, Illinois, and Massachusetts think they can control criminal’s access to magazines despite all evidence to the contrary.

    Personally, I wouldn’t run a printed mag in my AR, as it likely wouldn’t hold up over time (the plastic might melt as the gases fill the chamber). Likewise, I would only pull the trigger on a printed AR lower with a long string while the rifle is held in a bench rest. And don’t even think of printing an upper AR receiver, it will fail, and the results will be painful.

    Please do at least a little research before posting legal opinions, especially with regard to firearms. It makes for an epic fail when you don’t.

    1. Oops!  Sorry, folks.  I was under the impression that the AR-15 is a Title II firearm like the M-16.  I have updated the post accordingly.  

      1. Ryan Hamre says:

        You’re from California or New York aren’t you?

        1. Anonymous says:

          Sean lives in Texas.

          1. John Wood says:

            Texas?  I assumed TX laws would require you to own and carry a gun at all times?

        2. Anonymous says:

          Sean lives in Texas.

    2. DrewE says:

      > Likewise, I would only pull the trigger on a printed AR lower
      with a long string while the rifle is held in a bench rest. And don’t
      even think of printing an upper AR receiver, it will fail, and the
      results will be painful.

      Unlike other designs (such as the FAL) the AR-15 receivers are not involved in bolt lock-up (that comes from the bolt engaging an extension screwed on the rear of the barrel).  Plastic AR-15 lower receivers are commercially available (like the CAV-15 polymer part).

      A plastic upper with stock dimensions wouldn’t work well because there are a few pounds of steel barrel cantilevered off it.

      Other forces on the receivers are limited.

  9. Matt says:

    Your claim that printing an AR receiver “absent a federal license … is unambiguously illegal” in unambiguously false. Title 18 of the US Code states that an unlicensed manufacturer may make a receiver but may not sell it without a license. Many gun owners in the United States, myself among them, have chosen this method to obtain a firearm, with AR-15 and AK-47 variants being the most popular (they’re the easiest to make).

    A simple search for, say, “homebuilt AR receiver” would have turned up dozens of useful links for building a receiver from scratch, with photos from those who have done it, all posted without fear of federal prosecution.

    As far as the magazine issue goes, there is no federal ban on magazines, either by size, capacity, manufacturer, manufacture date, or intended firearm. State laws vary, with places like Virginia and Arizona being sensible, no restriction jurisdictions, while California, Illinois, and Massachusetts think they can control criminal’s access to magazines despite all evidence to the contrary.

    Personally, I wouldn’t run a printed mag in my AR, as it likely wouldn’t hold up over time (the plastic might melt as the gases fill the chamber). Likewise, I would only pull the trigger on a printed AR lower with a long string while the rifle is held in a bench rest. And don’t even think of printing an upper AR receiver, it will fail, and the results will be painful.

    Please do at least a little research before posting legal opinions, especially with regard to firearms. It makes for an epic fail when you don’t.

  10. Matt says:

    Your claim that printing an AR receiver “absent a federal license … is unambiguously illegal” in unambiguously false. Title 18 of the US Code states that an unlicensed manufacturer may make a receiver but may not sell it without a license. Many gun owners in the United States, myself among them, have chosen this method to obtain a firearm, with AR-15 and AK-47 variants being the most popular (they’re the easiest to make).

    A simple search for, say, “homebuilt AR receiver” would have turned up dozens of useful links for building a receiver from scratch, with photos from those who have done it, all posted without fear of federal prosecution.

    As far as the magazine issue goes, there is no federal ban on magazines, either by size, capacity, manufacturer, manufacture date, or intended firearm. State laws vary, with places like Virginia and Arizona being sensible, no restriction jurisdictions, while California, Illinois, and Massachusetts think they can control criminal’s access to magazines despite all evidence to the contrary.

    Personally, I wouldn’t run a printed mag in my AR, as it likely wouldn’t hold up over time (the plastic might melt as the gases fill the chamber). Likewise, I would only pull the trigger on a printed AR lower with a long string while the rifle is held in a bench rest. And don’t even think of printing an upper AR receiver, it will fail, and the results will be painful.

    Please do at least a little research before posting legal opinions, especially with regard to firearms. It makes for an epic fail when you don’t.

  11. Matt says:

    Your claim that printing an AR receiver “absent a federal license … is unambiguously illegal” in unambiguously false. Title 18 of the US Code states that an unlicensed manufacturer may make a receiver but may not sell it without a license. Many gun owners in the United States, myself among them, have chosen this method to obtain a firearm, with AR-15 and AK-47 variants being the most popular (they’re the easiest to make).

    A simple search for, say, “homebuilt AR receiver” would have turned up dozens of useful links for building a receiver from scratch, with photos from those who have done it, all posted without fear of federal prosecution.

    As far as the magazine issue goes, there is no federal ban on magazines, either by size, capacity, manufacturer, manufacture date, or intended firearm. State laws vary, with places like Virginia and Arizona being sensible, no restriction jurisdictions, while California, Illinois, and Massachusetts think they can control criminal’s access to magazines despite all evidence to the contrary.

    Personally, I wouldn’t run a printed mag in my AR, as it likely wouldn’t hold up over time (the plastic might melt as the gases fill the chamber). Likewise, I would only pull the trigger on a printed AR lower with a long string while the rifle is held in a bench rest. And don’t even think of printing an upper AR receiver, it will fail, and the results will be painful.

    Please do at least a little research before posting legal opinions, especially with regard to firearms. It makes for an epic fail when you don’t.

  12. Anonymous says:

    Oh, BS.  It is perfectly legal to manufacture your own weapon for personal use, and there is no “registration.”

    You can’t engage in the business of manufacturing for sale without a license.  But for personal use it’s done all the time, completely legally.

    How about doing some research before you wet pants and spout off?

  13. Anonymous says:

    There’s also nothing here you can’t do with a home mill, probably cheaper than the 3D printer, as well as more reliable, or, with effort, with a drill press and some clamps.

    1. If you know of a home cnc mill cheaper than $700 I would love to hear about it :)

  14. Rion says:

    Correction – you must have a license to manufacture firearms FOR SALE. You can, in most states, however, build anything that you would otherwise have been able to buy. If you’re a felon, for example, you cannot build a firearm, since you can’t purchase or possess one legally. Also, automatic weapons and destructive devices are banned explicitly. There’s a plethora of forums, especially ones like CNCguns.com, that allow users to learn how to build their own firearms – generally in a responsible and educational manner.

  15. Doug Johnson says:

    Next come the laws that don’t work and then finally we are in “Rule 34″ by Charles Stross.
    Not saying that I think that making a large magazine for an AK-15 is a good thing, just that trying to stop people from making them by legislating the process is a losing game.
    Read the novel, it’s good…scary.

  16. Robert K says:

    There is nothing wrong with making a firearm. Thousands and thousands of people buy what are called “Flats”  It is stamped sheet metal that they bend into shape and do final drilling on that lets them make a AK receiver. Then the barrel and furniture are added. It allows someone to Make a high quality AK-47 for under $300. There are also AR15 kits also

  17. Robert K says:

    There is nothing wrong with making a firearm. Thousands and thousands of people buy what are called “Flats”  It is stamped sheet metal that they bend into shape and do final drilling on that lets them make a AK receiver. Then the barrel and furniture are added. It allows someone to Make a high quality AK-47 for under $300. There are also AR15 kits also

  18. Patrick Tait says:

    I will say that I can’t really blame you for being ignorant of gunlaw as there is a good deal of FUD out there, but still, no need to keep spreading it.  And you can’t really make something specifically advertised as a disruptive technology without something like this happening eventually. 

    1. Thank you, Patrick. Your tone is appreciated.  I have made a correction to the post, above.  

    2. Thank you, Patrick. Your tone is appreciated.  I have made a correction to the post, above.  

    3. Jeremy Nimmo says:

      Good to see a reasonable tone on a potentially contentious piece of machinery like this.

  19. Jay Kominek says:

    the S&W M&P15-22 is .22LR and both receivers are plastic. In fact I think everything but the barrel and springs is plastic. MidwayUSA’s catalog is just full of 22 rimfire barrels and assorted springs.

  20. Jay Kominek says:

    the S&W M&P15-22 is .22LR and both receivers are plastic. In fact I think everything but the barrel and springs is plastic. MidwayUSA’s catalog is just full of 22 rimfire barrels and assorted springs.

  21. Jay Kominek says:

    the S&W M&P15-22 is .22LR and both receivers are plastic. In fact I think everything but the barrel and springs is plastic. MidwayUSA’s catalog is just full of 22 rimfire barrels and assorted springs.

  22. Jake A. says:

    In the US, there are no national restrictions on magazine capacity, only a few states like California and Massachusetts have restrictions (and some of those, like Maryland’s, are only on the sale of “high-capacity” magazines; importation, i.e. driving across the border to VA to pick up some 30 round magazines is perfectly legal).

    I might take issue with the magazine spring losing stiffness over time as well, though I don’t know how plastic would react differently. With ordinary magazines, it is loading and unloading a magazine that causes the spring to lose stiffness; you could store a loaded magazine for a hundred years, and barring anything like rust it would still function perfectly.

    One rebuttal to the legality of manufacturing a firearm for personal use: you can easily buy an 80% complete receiver (around $80, do a Google search for “80% AR-15 receiver”) and just complete some of the final milling operations yourself. When it’s shipped to you, it’s not a firearm (the ATF has actually specifically addressed this) and is therefore, legally, just a block of aluminum. This is the same as the AK “flats” mentioned by other commenters. The mechanical/structural aspect of the lower receiver is a bit more interesting; the lower receiver actually take very little if any of the stress of firing the gun, so doesn’t need to be physically very strong to be fully functional. Heat shouldn’t start to affect it unless you’re firing far more frequently than normal, even in actual combat. The only strength that is necessary is to keep it together in rough conditions – the plastic might break if you fall on it or drop it off a building, while an aluminum receiver shouldn’t get any more than a scratched finish.

    I do want to say, I appreciate your willingness to post what could be seen as a sensitive topic. In my opinion, much of the culture of gun enthusiasts overlaps with maker culture – people modifying things to work better, or building from parts (like ordinary, non-plastic AR-15s), or even a few people building largely from scratch. Espousing such common ground can only help both cultures.

  23. Jake A. says:

    In the US, there are no national restrictions on magazine capacity, only a few states like California and Massachusetts have restrictions (and some of those, like Maryland’s, are only on the sale of “high-capacity” magazines; importation, i.e. driving across the border to VA to pick up some 30 round magazines is perfectly legal).

    I might take issue with the magazine spring losing stiffness over time as well, though I don’t know how plastic would react differently. With ordinary magazines, it is loading and unloading a magazine that causes the spring to lose stiffness; you could store a loaded magazine for a hundred years, and barring anything like rust it would still function perfectly.

    One rebuttal to the legality of manufacturing a firearm for personal use: you can easily buy an 80% complete receiver (around $80, do a Google search for “80% AR-15 receiver”) and just complete some of the final milling operations yourself. When it’s shipped to you, it’s not a firearm (the ATF has actually specifically addressed this) and is therefore, legally, just a block of aluminum. This is the same as the AK “flats” mentioned by other commenters. The mechanical/structural aspect of the lower receiver is a bit more interesting; the lower receiver actually take very little if any of the stress of firing the gun, so doesn’t need to be physically very strong to be fully functional. Heat shouldn’t start to affect it unless you’re firing far more frequently than normal, even in actual combat. The only strength that is necessary is to keep it together in rough conditions – the plastic might break if you fall on it or drop it off a building, while an aluminum receiver shouldn’t get any more than a scratched finish.

    I do want to say, I appreciate your willingness to post what could be seen as a sensitive topic. In my opinion, much of the culture of gun enthusiasts overlaps with maker culture – people modifying things to work better, or building from parts (like ordinary, non-plastic AR-15s), or even a few people building largely from scratch. Espousing such common ground can only help both cultures.

    1. Sean says:

      There was a dude using a cutting board to make an AR-15 lower “http://230grain.com/showthread.php?31611-Homebuilt-HPDE-AR15-Lower”. 

      The AR-15/M-16 family of firearms uses a system where the bolt locks into the barrel extension, thus reduces the stress on the lower receiver enough so that it only acts as a frame to hold all other components in alignment.  Madness or genius, that is still being debated.

      1. Jake Bullard says:

        That’s cool. I thin he did one out of wood to.

      2. Jake Bullard says:

        That’s cool. I thin he did one out of wood to.

  24. Joe says:

    I believe the author to be misinformed about
    manufacturing a firearm.  As long as you do not sell it I believe it to
    be legal. There was a company from Montanta that sold the blanks to
    manufacture all sorts of weapons legally.

  25. Joe says:

    I believe the author to be misinformed about
    manufacturing a firearm.  As long as you do not sell it I believe it to
    be legal. There was a company from Montanta that sold the blanks to
    manufacture all sorts of weapons legally.

  26. Alberto Knox says:

    It is absolutely legal to build your own AR-15 or other firearm from scratch.  No federal licensing or registration is required.  some states have specific requirements but most have none.  You need a manufacturers license if you make it to sell.  http://www.thefirearmblog.com/blog/2010/02/22/diy-ar-15-lower-receiver-tutorial/

  27. Anonymous says:

    In most states, except CA, high capacity magazines are perfectly legal. There are enough old AR-15 magazines kicking around that more people probably have them in CA than want them. I have several pre-ban mags that I obtained when they were legal but expensive. FWIW there is little use of ‘assault weapons’ in the USA in crime, hand guns are so much easier to carry and conceal. Even in CA the various legal judgments about “off list lowers” means that there is no practical limitation on obtaining and using AR-15s and AK-47s, tens of thousands have been sold in the last few years. Interestingly there has been no associated rise in crime. CA can not deal with the off list lowers without adding all the currently legal limited weapons with fixed (as fixed as a bullet button really is) magazine to the assault weapon registry and thus de-restricting them. You can even buy CA legal complete weapons in many gun shops. My friends take shooting trips to Nevada when they want to make use of their toys without fear or restrictions, but the dirty little secret is that they are all five minutes from being full on semi-auto-only AR-15s.

  28. Thebes says:

    PLEASE learn your facts before you blog.

    Guns in the USA, except for NFA weapons like machine guns, are NOT registered. Only one state, Hawaii, registers all guns within it. Several states require firearm owners to register but do not register individual long guns.

    It is ENTIRELY LAWFUL under Federal Law for an individual to manufacture his or her own firearm so long as it is not done with commercial intent. That includes an AR-15, or even a “silencer” though the later must be federally registered and a tax paid. A few states and other jurisdictions do ban such manufacture and indeed even possession of certain firearms.

    1. Are you sure?  My understanding is that Title II firearms, such as “machine guns,” require registration and tax stamps and so forth, even if you’re manufacturing just for personal use.  

      1. Jay Kominek says:

        Title II stuff requires you pay a special tax for the transfer or manufacture, yes. The laws were changed in 1986 so that no new machine guns can enter civilian circulation, whether you make it yourself or not. So there’s 186000 of them or so, and that’s it (for now). SBR’s, SBS’, destructive devices, AOW’s and suppressors are all fair game at the federal level, with just the tax stamps you’re referring to.

        I don’t remember if the lower receiver requires any modifications to be used as part of an M-16; the big differences that come to my mind are in the trigger group. There’s a lot of cross over in parts, either way, but so long as you don’t have all the parts necessary for full auto, you’re generally fine.

    2. Are you sure?  My understanding is that Title II firearms, such as “machine guns,” require registration and tax stamps and so forth, even if you’re manufacturing just for personal use.  

  29. Thebes says:

    PLEASE learn your facts before you blog.

    Guns in the USA, except for NFA weapons like machine guns, are NOT registered. Only one state, Hawaii, registers all guns within it. Several states require firearm owners to register but do not register individual long guns.

    It is ENTIRELY LAWFUL under Federal Law for an individual to manufacture his or her own firearm so long as it is not done with commercial intent. That includes an AR-15, or even a “silencer” though the later must be federally registered and a tax paid. A few states and other jurisdictions do ban such manufacture and indeed even possession of certain firearms.

  30. Witt Sullivan says:

    To convert an AR-15 to fully automatic requires the receiver to be modified to accept the extra parts enabling fully automatic fire, but modifying it in that way is illegal and counts as manufacturing a machine gun, which is illegal unless you have a license to manufacturer firearms. There are legal parts that can make any AR-15 fire automatically, but they’re so scarce they cost as much as a pre-1986 M-16 or AR-15 conversion, $10,000 or so.

  31. Bucky says:

    Not all shootings and rampages happen in California. So why only in California for strict gun laws?

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