Justin Kelly opened the door for his postman on what he presumed to be a routine package pickup. But this time the postman brought the local postmaster, who handed Kelly a letter demanding he stop shipping weaponized toys to Singapore or risk extradition.

Despite the seriousness of the allegations, Kelly and the postmen had a good laugh. Several weeks before, Kelly had mailed a Nerf blaster modification kit to Thailand, and customs in Singapore caught it when it routed through there. The kit was designed to increase the battery power flowing through the receiving blaster, boosting its firing strength. Aiding one man’s quest to launch foam darts a few more feet had landed Kelly under Postal Service monitoring for three years.

Kelly learned his lesson. As the founder of blaster-modding firm LaserGnomes, he now puts limits on how far and fast his mods will fire darts. Every year he ships about 600 Nerf blasters and parts all over the world from his office in Emeryville, California. His best-known part, the SlugFire, allows the three-dart Nerf Sledgefire shooter to channel all three barrels of firing power into one huge dart, or any other type of dart. Another modification combines the bodies and parts of three Nerfs into one with a custom mechanism that allows you to both cock and fire it by pumping the handle. Kelly has also been known to customize Nerf blasters to look like props from video games, or whatever else a customer requests.

Enthusiasts began experimenting with modifications soon after Nerf released its first blaster model in 1989. Simply replacing the spring that sits behind a Nerf dart can extend its range. But Kelly is part of a growing group offering a new modification option that would have been impossible even 10 years ago: He 3D prints parts. The result is the potential for greater customization, more experimentation, and the ability to adapt to whatever the Nerf community demands.

AN INFECTIOUS HOBBY

When chemical engineering student Eric Beitle was a freshman at the University of Arkansas, his dorm was a battleground. Epic Nerf fights broke out on the regular as students sought release from school-induced stress.

“Somebody would buy the new next greatest thing and somebody else would buy the new next greatest thing,” Beitle says. “It almost turned into a bit of an arms race because we were all rather competitive.”

Beitle’s response was to begin modifying his battle weapons. He greased insides to help the darts move more smoothly. He attached different barrels to convert one blaster into a close-range shotgun. He bought a SlugFire from Kelly and began shooting large darts.

Beitle, now a sophomore, has since joined his campus’ Humans vs. Zombies scene, where hordes of foam sword-carrying “zombies” strive to tag other students, turning them into the undead too. The students can shoot zombies with a Nerf blaster to freeze them for 15 minutes.

Blasters that shoot farther and faster, and those with more ammo compatibility, are obviously an advantage. As a result, modded blasters have become a staple in the games.

Many Humans vs. Zombies games begin with a rule that players can only use single-shot blasters. That includes Nerf’s Sledgefire, a design that’s relatively boring and low-power — until you add a LaserGnomes SlugFire mod.

“We took a poorly received blaster and turned it into the must-have of any HvZ competition,” Kelly says. Some Humans vs. Zombies chapter leaders, finding the modifications unfair, have even complained to LaserGnomes.

Modded Nerf blasters are hugely popular overseas on continents like Asia and Australia, where people like Kelly’s Thai customer have to work around strict laws that ban airsoft, paintball, and even high-powered projectile toys. People lusting after guns seek out whatever substitute they can, which often leads them to the Nerf modding community. Kelly estimates that at least half of his orders come from abroad.

Greg Heffner, who runs another Nerf 3D printing service called 3D Printed Solid, began selling a mount for Nerf accessories last year. Since then, his website has expanded to carry more than 70 products. He sells 3D printed camera mounts and dart holders, plus custom blasters.

“There is a good amount of experimentation and development done by young enthusiasts and they take pride in their work,” Heffner says. “The parts are small and simple in design. Contrary to injection molding, you can create, modify, and adjust your designs in a short period of time.”

REVENGE OF THE NERF

“LaserGnomes started for vengeance, which is I guess a bad way to start things,” Kelly says. One day in 2012 his roommates attacked him in their apartment with Nerf blasters, and he decided he needed to retaliate.

Kelly bought an Alpha Trooper, a classic-looking Nerf blaster capable of shooting from a clip of 12 or more darts. He painted it with camouflage colors and attached a GoPro and a laser pointer. The entire contraption was held together with duct tape and glue.

He got his revenge, but in the process discovered an intense online community of Nerf blaster modders and began to fall deeper into the field. Six months later he acquired a 3D printer from Type A Machines.

At the time, Kelly was a 3D animation and visual effects student at Academy of Art University in San Francisco. When a class challenged him to put together a mock company, he decided to build a real one instead: LaserGnomes. (The name “comes from the combination of innovative technologies — lasers — for the betterment of the environment through mindful designs and applications — gnomes.”) The initial idea was to collect Nerf blasters and repair them or harvest them for parts, but it soon grew to encompass custom accessories and modifications.

“Being able to mount a GoPro in a very specific way was one of the first things we did. Then, taking two different blasters and merging them into one. We started getting requests like ‘Can you make it look like ‘Halo,’ or ‘Fallout,’ etc.,” Kelly says.

Kelly refined his 3D printing chops as one half of Mind 2 Matter, a now-defunct 3D printing and metal casting service that ran out of the Bay Area Advanced Manufacturing hub in San Leandro, California. Kelly split with his co-worker and the center and founded Proto.House, a 3D printing on-demand service.

Today, Kelly runs Proto.House and LaserGnomes out of his 600-square-foot lofted workspace, which sits above the dusty office of SoulMind, a CNC milling and laser etching service. Flowtoys, which makes colorful batons and juggling clubs, also shares the workspace, with plans for Proto.House to begin 3D printing some of its parts. It’s a cozy and collaborative-feeling space where experimentation feels key to everyone’s business plan.

USING FRACTALS AS FEEDBACK

When Kelly set out to build the SlugFire dart adapter, he could have made precise measurements of a Nerf blaster’s existing parts and replicated them. But Kelly likes to practice what he calls fractal design: draw up plans for many variations on the same part, and then make them all. He likes to print many versions of a part at once so he can test the effects of minute changes in his designs, looking for a balance of power and accuracy. Then he takes the best-performing option and tries more designs based on it.

Kelly’s Nerf creations all start out on paper. He measures with calipers anything the part is meant to replace or attach to, and then eyeballs the rest. Occasionally he will 3D scan a part, but the output tends to be more of a reference than a final product. Instead, he builds 3D designs by hand in Tinkercad.

For SlugFire, Kelly began with seven different 3D prints of possible designs.

“We were trying to capture the most air, but I wasn’t sure what size the barrel needed to be,” Kelly says. “Instead of measuring or using complicated math, I just printed seven different versions and tested them empirically, and then with that answered moved forward.”

Kelly had his team of interns refine the SlugFire further by measuring the firing speed of each design iteration with a chronograph. At one point, a dart clocked just over 100mph, fast enough to break glass — not to mention skin.

“We knew we had something that was both amazing and not suitable for the public,” Kelly says. The final version of

the SlugFire had toned-down firing power, which allowed it to be safer and more accurate.

Since that first version of the SlugFire, it has changed continuously. When a customer breaks something from LaserGnomes, Kelly asks for it back. He examines the damage and integrates improvements into the design so future pieces that go out are more durable.

This process of iterating on small design changes over and over again would take months, and likely be cost prohibitive, if not for Kelly’s army of 3D printers. On a weekday in early November, Kelly had 12 LulzBot Minis printing parts simultaneously. They are all manned via a central Raspberry Pi controller Kelly programmed himself, since out of the box LulzBots can normally only be controlled one at a time.

THE QUEST FOR COMPATIBILITY

If you were a child in the 1990s or 2000s, there’s a good chance you spent some time running around with a Nerf blaster in hand. But if you bought one today and brought it home to use with your vintage Nerf dart collection, you’d make a harrowing discovery: Most of the darts won’t fit. Hasbro switches darts’ lengths and widths frequently, forcing you to buy new darts for new blasters. Remedying that is one of LaserGnomes’ other focuses.

“My product allows you to reload any dart you want. You could even be using off-brand darts. You could be using darts from the 1990s,” Kelly says. “You load it in there and now you can fire it.”

Let’s say that you want to use one of your old Nerf blasters. If even a tiny part breaks, you might think your only choice is to toss out the whole thing. Hasbro doesn’t sell replacement parts or make its designs particularly easy to crack open for repairs. The oldest Nerf blasters are slowly disappearing as they break one-by-one, and Hasbro nudges people toward buying a replacement instead.

Kelly’s armory contains a 1995 Nerf Crossbow, an iconic wine and teal colored dart-shooting bow. Today it is one of the rarest of all Nerf shooters, meaning the remaining units are too expensive to buy just for harvesting parts. Kelly’s came with a snapped part, but he was able to repair it thanks to 3D printing.

Kelly doesn’t share his printable performance-enhancing modifications. But he does share legacy replacement part designs. “Ultimately, I envision inspiring enough people that someday there’s a collection of online design files that are just open, that Hasbro just charges a dollar a download or just gives it out,” Kelly says.

STAYING AHEAD OF HASBRO

Hasbro, which has only responded to Kelly’s work with favorable comments on social media, seems to be catching on to the desires of the community, offering new products like the Modulus, a 2015 blaster that can be modified with interchangeable handles, clips, and more. The company is also selling gaming-friendly blasters that shoot balls capable of traveling farther and faster than darts. Between Hasbro’s recent debuts and the efforts of modders, Nerf blasters have a new appeal for children, teenagers, and grown-ups alike. Adults can modify their old favorites to suit modern needs or trick out models still available on store shelves.

The addition of balls, plus other trends such as increasing power usage in blasters, is keeping Kelly alert for changing customer requests. But as long as clients find Hasbro’s Nerf offerings lacking, LaserGnomes will be in business.