RX-27 Handheld Magnetic Acceleration Cannon


Active Member
Hello 405th! It’s my great pleasure to bring you a completed project that I started nearly 8 years ago. The RX-27 Handheld Magnetic Acceleration Cannon (HMAC) is a primarily 3D-printed prop of my own design inspired by the weaponry of Halo. Let’s dive right in!


Every great weapon needs a great carrying case.


And now with the lights on!


Next is a close up of one of the “acceleration units”. These three repeating elements are probably my favorite feature of the HMAC with sharp angles, clean lines, and a fun blend of colors. I used painter’s tape and window frosting spray to achieve the pattern on the plexiglass, and a blue bendy straw inside to diffuse the light. You can also glimpse the barrel cap that I 3D-printed in transparent plastic.


Due to its length, the HMAC uses an anti-gravity stabilization system in place of a bi-pod. The design is loosely based on the Halo 3 gravity hammer, specifically the little glowing blue nubs on the front of the hammer.


In all my props I like to include witty warning labels. They were custom made in MS Word and printed on white sticker paper. The little red triangles and electricity warning on the accelerator unit were also made this way. Finally, the tube on the top right is lit by UV LEDs and fluoresces instead of just regular blue LED illumination.


A close up of the scope shows the sun-glass lens placed in the front, etched with an exact-o knife similar to my JFO helmet. Thanks to Carpathia for this little trick!


This area has a lot going on. It’s the merger of about 6 major pieces (scope, barrel, magazine holder, heat sink, mid receiver and main receiver) and what can’t be seen is the intricate sliding, locking, and screwing mechanisms that fit together like an intricate puzzle.


The name RX-27 HMAC comes from a few different things. I used the RX from my favorite Gundam, the RX-0 Unicorn Gundam. 27 is my favorite number. Magnetic Acceleration Cannons or MACs are the main weapon for large UNSC fleet ships from Halo, so I threw an H in front and there you have it.


The “batteries” here actually hold the 12 AA’s that power the HMAC. The warning label here also has a little nod to the Chief.


A rear view of the gun shows off the illuminated scope. This part was inspired by the Halo assault rifle and even has a compass and round counter decal similar to the Halo 3 version.


The three accelerator units.


I also printed a few “rounds” that the HMAC would theoretically fire. Similar to the US Navy’s rail-gun, the HMAC’s round consists of an outer shell that helps accelerate the round to near Mach 10 speeds, and an explosive round that travels down range.


A few shots of me with the gun.




I’d like to give a huge thanks to my close family friend Ed, who lent his workshop, his expertise, and an incredible amount of time working on the HMAC. He never understood the desire for “battle damage” or in his words, “messing up a perfectly good piece of art”. So here he is holding a pristine version of the HMAC before weathering.


And also a big shout-out to my mom for being my mom.


I’d also like to thank my good friend Vince for his amazing pictures, my friend Cameron for his continuous support in prop-making, my sister for her generous gift of a 3D-printer last Christmas, my girlfriend Sarah for putting up with long nights of building, and all my roommates for dealing with the constant whir of my printer in the living room.

I also made a brief video of the finished gun showcasing the electronics. I forget to show it in the video, but the other sounds are random movie quotes (“I am your father”, “I’ll be back”, “ET phone home”, etc.) and a bit of the Halo 3 soundtrack. Stay tuned for a follow-up post after the video for progress pictures and the story of constructing the HMAC.



Active Member
Constructing the HMAC: From Idea to Reality

The HMAC started as an idea close to 8 years ago. After numerous iterations on spare pages of school notebooks, I drafted a schematic ca. 2012 that would remain largely unchanged for the next 6 years.


From this schematic, I constructed a 3D-model in Sketchup.


And used the model to create 2D-templates for constructing the gun in cardboard.


Progress was extremely slow, and after 5 or so years I had still yet to figure out a structural support system for the HMAC. Enter the 3D-printer in December 2017, a Monoprice Maker Select Plus.


I remodeled the HMAC into printable components that would be held together with metal screws, sliders, tabs, and epoxy.


Many, many hours or printing later and I finally finished all the parts! A few other details popped up here and there during the construction, but they were all minor additions.


The completed print next to its obsolete cardboard cousin.


During the print, I had lots of spare time on my hands, so I began some of the electronic testing. Here’s the diffusion testing using a straw and frosted plexiglass


Below is a picture of aligning the main barrel assembly and the main receiver for a few more structural screws. It also shows the red spot putty used to smooth the 3D-printed texture of the parts.


Base painting continued, with the appropriately frosted plexiglass for the accelerators and finished barrel piece.


It was at this point that Ed and I discovered the blue acrylic tube fluoresced under UV. A really cool effect!


Further base painting with scope attached via small 3D-printed connectors


Finished Base Coat!


The first barrel and lower barrel hold light test. Successful!


The final wiring of the electronics in the rear receiver. Fitting all the wires, switches, regulators, and attachments was a bit challenging. Appropriate wire management is essential!


A fun little comparison between the Sketchup model first-person view…


And the completed version.


It’s been an amazing journey taking an original idea and turning it into reality. I’ve learned a lot about electronics, 3D-printing, tolerances, and general prop construction along the way.

Better equipped and more knowledgeable, I begin my renewed foray into armor construction. In the background is Steve Jr., my armor dummy. In the front are my completed works so far, a finished Halo Reach Combat Knife, Gungnir Knee Pads, 3D-printed hand plates and JFO Helmet.


Finally, here's the link for the full album of photos: RX-27 HMAC

Thanks for reading! I’m glad I could share this with you all and can't wait to share more in the future.


This is amazing! It looks so cool, and it's even cooler that it's your own original design. The scientific reasoning behind some of the design elements is a nice touch.

Lieutenant Jaku

Well-Known Member
Amazing work man, I know how designing your own weapons is and it feels amazing to see your ideas become reality.
do you happen to have the 3d files available or are you selling them?
if you arent giving them out though thats okay


Active Member
THIS IS ABSOLUTELY AMAZING! WOW! I would make on but I don't want to take 8 years :b great job!
Thanks Dash! Hopefully the next one won't take so long now that I have a little more experience.

That is absolutely inspiring!! Unbelievable what can be created by committing to a craft. I don't think anyone here can clearly express how awesome this. Great work!

Thank you Matt, I'm glad I can help inspire the community that inspired me! (y)

This is amazing! It looks so cool, and it's even cooler that it's your own original design. The scientific reasoning behind some of the design elements is a nice touch.
Thanks! Gotta justify the need for all the shiny lights!

Amazing work man, I know how designing your own weapons is and it feels amazing to see your ideas become reality.
do you happen to have the 3d files available or are you selling them?
if you arent giving them out though thats okay
I do plan on releasing the 3d files, however they need a little bit of cleaning up and re-working given what I've learned about tolerances, a few small sizing mistakes etc. In addition, I'm wondering if there's any way to make them exclusive to the 405th (through the armory for example)? Not sure if I plan on releasing them generally to the public yet but I'd be more than happy to give them out to you all.

If anyone knows who to contact or has any insight on how to get the files on the armory/elsewhere on the 405th, let me know!