Featuring all the basic elements of human survival, including taxing physical struggles in the woods, harrowing split-second tactical decisions, and danger at every corner, paintball is both a popular sport and a thrilling way to spend the afternoon. You might be inclined to think it is the domain of adrenaline-charged brutes, but what happens when an engineer crosses into this realm?
I know of such a man and his legend. While others are content to carelessly squander ammunition in some variation of shock and awe, he approaches with the cold efficiency of a ninja: compact, surgical, and quite deadly. He'll clear a team with a couple of 8-shot pistols in near silence. But to hone one's skill in such a way requires care of your weapons in much the same way a Tamahagane sword smith might care in 1571. So what's in the toolbox of a 21st century paintball ninja? Why CAD and 3D Printing, of course.
Design Analysis
One particular marker (that's paintball speak for the “gun”) the ninja keeps in his diverse arsenal is the AGD Automag classic. The Automag is arguably the greatest paintball marker of all time, despite it's nearly 25 year heritage. While the core of this particular instrument has withstood the test of time, available accessories have languished, and some recent innovations are simply incompatible.
Case in point, the barrel system originally designed with a "twist lock" mechanism to enable rapid disassembly, just doesn't work with today's widely available threaded barrels. To add further insult, the rapid disassembly advantage for which the original barrel was designed for is no longer relevant on today's Paintball battlefield. Adapters for modern barrels are available, but they are inelegant solutions costing additional weight, and certainly not befitting a ninja.
Of further concern was the "rail" of the original marker, a component that sits between the marker's main body and the grip frame. The original rail was quite heavy, and used an older version of the firing mechanism, long since abandoned. While newer rail pieces were decidedly lighter weight, they also lost foregrip compatibility vital to the ninja's steady aim. Our contemporary ninja found himself at a crossroads, and it was clear that the solution must be of his own design.
Time for some, er, ninja-ing.
Marker Maker
The paintball ninja, having once been a programmer before being properly reincarnated, prefers OpenSCAD for his model-jitsu. Using OpenSCAD, he designed a superior barrel adapter to conserve weight, and added slots to the threaded section to get around the original marker's "twist lock" retainer pin. He also purposefully undersized the threads such that the adapter (if manufactured from plastic) would behave like an expanding collet once the barrel piece is threaded in place to lock the assembly.
Threads were generated in the OpenSCAD model using a screw library hacked up by Aubenc of Thingiverse. The new adapter design also provides the added advantage of allowing the breech (the opening thru which the paintball ammunition is loaded into the barrel) to be rotated in any direction, allowing for creative feed configurations. A further modification of the breech shape allows the chambering of shaped rounds, common ammunition of choice for a ninja. For the rail, the redesign involved adapting to contemporary firing mechanisms, but still preserving the compatibility with vintage foregrips. Built from plastic, the new rail would also sport a further weight advantage. Hai.
Enter the 3D Printing Dragon
Ninjas of old dutifully awaited the meticulous handcrafting of their weapons, but manufacturing is a little bit different these days. For the barrel adapter, the ninja chose the art of nylon Selective Laser Sintering (SLS) as the preferred process due chiefly to design complexity – though later iterations of the design might be possible as a multi-piece fabrication using a filament printer or even injection molding.
The nylon process provided enough flexibility for the collet feature, all while saving weight and reducing cost from a conventional steel design. The new rail was also printed with SLS again for a substantial weight savings over a similarly spec'd aluminum variant. While the nylon rail isn't as strong as the aluminum equivalent on its own, once it's incorporated in the assembly it delivers similar strength. 3D Printing proves it is honorable and worthy.
The end result is a weapon truly worthy of a ninja, but also earning props for engineering. A true ninja must tirelessly train to continuously improve his own physical skill and mental acuity. Such assets are invaluable on the battlefield. Who would have ever thought that CAD would be the new-age shuriken? But this is only the beginning, the ninja honor demands that he abide by the code of the engineer and continue to evolve his weapons.
So join us next time on Paintball Ninja for further adventures in marker design including some rotary loading adventures.
A Part Number Anthology 
Part numbering. For most engineers, this two-word phrase is all it takes to conjure up especially strong feelings about what it means to be “right”, and what it means to be very, very “wrong.” We've assembled a handful of our part number greatest hits in this eBook anthology.
