Nerf blasters are fun and all, but they’re limited by the fact they have to be safe for children to play with. [Flasutie] faced no such restrictions when building his giant 40 mm foam dart launcher, and it’s all the better for it.

This thing is sizeable—maybe two to four times bigger than your typical Nerf blaster. But that’s no surprise, given the size of the foam ammunition it fires. [Flasutie] shows us the construction process on how the 3D-printed blaster is assembled, covering everything from the barrel and body assembly to the chunky magazine. Loading each round into the chamber is a manual process, vaguely akin to a bolt-action mechanism, but simplified.

It’s the method of firing that really caught our eye, though. Each round has a cartridge and a foam projectile. Inside the cartridge is a quantity of flammable HHO gas generated, presumably, from water via electrolysis. The blaster itself provides power to a spark gap in the cartridge that ignites the gas, propelling the projectile through the barrel and out of the blaster.

We’ve seen plenty of Nerf blasters and similar builds around these parts, including some with a truly impressive rate of fire. Video after the break.