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Welcome to the fifty-fifth installment of Your Comments. Here are our favorites from the past week, from Makezine, our Facebook page, and Twitter.

In the article 3D Printed Gun Fires Real Bullets, R Buchman says:

Before anyone gets worried about 3D printing working guns, it should be kept in mind that all the actual “shooty” bits – the chamber, barrel, breech, etc – are in the upper receiver, and the one used here is a real one. To put it another way, all the important parts that shoot the bullet are from a real rifle, all in one piece.

In an AR patterned rifle (which this is) ammunition is loaded into and fired from the *upper* receiver (not the *lower* receiver, which is what was printed here.) The lower receiver is subject to relatively low stresses and is not where any of the actual bullet-shooting part happens. The lower is the stock and trigger and holds the magazine. The upper is the barrel and chamber and all the parts that go BANG.

People have made working lower receivers out of wood (as opposed to 3D printing one), just to prove it can be done. Build a lower out of wood or plastic (or 3D print one…) and stick a “real” upper on it, and there you go: working rifle.

This isn’t to diminish how interesting it is to 3D print a working lower; but if you don’t know much about firearms it’s easy to jump to conclusions.

Also, in the USA it is perfectly legal to build your own firearms. (If you want to sell them then that’s something different, though.)

In the piece MAKE Asks: Raspberry Pi Projects, djnastyc remarks:

A coworker and I are working on a coffee monitoring system, which includes a webcam and several sensors connected to the R-Pi, which communicates via HTTP with our company’s workflow software. The Pi monitors coffee pot temperature and position and sends an email or SMS notification when it thinks there’s a fresh pot of coffee. A webcam provides the opportunity for visual verification of the coffee status.

In the article A PrintrBot Fixed My Dishwasher, Facebook user Taylor House says:

I think I may have to buy one in time for the holidays… so I can print out some plastic forks and knives.

In response to How-To: Daisy Chain Arduinos Via Serial, mupeg says:

Wow Scott, nice work! I think I’m going to have to try this out tonight. This kind of thing (needing to communicate between a host server and multiple micros simultaneously) come up for me pretty often and this is much more elegant than my solutions. Cheers for sharing!

In the article Wired Italy’s Video Profile of Arduino Co-Creator Massimo Banzi, Steve Sparks comments:

I had a Lectron set when I was four, and it has had a MASSIVE impact on the hardware/software nerd I am today. Last year I went through a lot of trouble to get a start kit from to give to my children when they turn four.

In the article Pittsburgh Tech Shop is Hiring, Christian Restifo says:

I cannot wait for them to open. I went down there at lunch the other day to check it out. I saw a freshly boarded over area that I assume is the site under construction. I wanted to drill a hole in the OSB so I could see inside.

Like these comments? Be sure to sound off in the comments! You could be in next week’s column.

Michael Colombo

In addition to being an online editor for MAKE Magazine, Michael Colombo works in fabrication, electronics, sound design, music production and performance (Yes. All that.) In the past he has also been a childrens’ educator and entertainer, and holds a Masters degree from NYU’s Interactive Telecommunications Program.



  1. M4A1 AEG, over 200 parts and can be operate in automatic or manual without power! Pretty cool

  2. Guy says:

    Why in the world should anyone ‘get worried’ about this? When a trip to the hardware store can yield much more destructive results, it’s clear someone going through the effort of printing multiple prototypes probably doesn’t have malicious intent.

    Guns are OK; they’re just tools, and like any other tools, it’s about how you use them.

    Check out Doan Trevor if you want to see some REALLY impressive making.

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