January 29, 2026
Description
Firing demo:
How it works:
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
When you see the letters "HPA" or "High Pressure Air" in the Nerf hobby, it is referring to a blaster that uses compressed air to fire a dart, very similar to how paintball markers work.
The air is stored in an external tank at a high pressure (~3000psi), and then goes into a regulator which brings down the pressure to a usable range (I use 100psi on my blasters. Some others use 150psi).
The regulator then feeds the air into a hose which leads to a valve, and then that leads to the air tank onboard the blaster, otherwise known as a "HPA Core", "HPA Tank", or "Air Tank". That HPA core is what actually holds the air which is used whenever the blaster is fired, with each shot emptying the HPA core's air behind a dart in a barrel, launching the dart out the front!
HPA is used as a distinction from "LPA" or "Low Pressure Air" blasters. LPA blasters are the sort of things you might've played with as a kid; they have a manual pump that you slide back and forth to charge up the air tank, and then you pull the trigger to fire a shot.
The difference between LPA and HPA blasters is pretty much all in the way they are fed with air. In LPA, you need to manually pump air, with your hand, into the blaster before each shot. With HPA, there is no manual action needed. You just pull the trigger to fire!
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
HPA blasters are pretty much the pinnacle of performance when it comes to dart blasting.
HPA blasters can match the FPS and accuracy of spring powered blasters, while also having the rate of fire and compactness of flywheel powered blasters.
Additionally, if you are already a person who owns paintball markers or airsoft guns that use compressed air tanks, the buy in cost for an HPA blaster is SIGNIFICANTLY less daunting overall.
While HPA can't match the price of springers or flywheelers, it is a very fun section of the hobby in my opinion!
I personally run this blaster at 100psi from the regulator for ~150FPS dart speed cap games. You can definitely use more PSI and a longer barrel to get WAY higher FPS (the Cosmic Nomad HPA core is capable of well above 250 fps with the correct setup).
(just make sure that your club and area allows it)
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
This is not legal advice.
Many areas of the USA and some parts of the world restrict compressed air powered toys, such as paintball and certain airsoft guns. HPA dart blasters are very likely to fall under the same restrictions.
Before purchasing, building, or using any HPA dart blaster, make sure that you can do so legally in your location.
Additionally, some clubs do not allow HPA blasters. Make sure that you are allowed to use them at your intended venue and group BEFORE buying, building, or using these blasters.
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
Now, the major problem with HPA is the cost: as it is currently, HPA has a high upfront cost, and costs more than most flywheel or spring powered dart blasters. The following text is a copy/paste comment that I use whenever someone asks me about how much it costs:
The cost of a whole HPA setup heavily depends on exactly which parts you buy from where.
The air regulator I use is ~$200 new, but I got mine used for ~$100. It's an old version of the Wolverine STORM Airsoft regulator.
The supply bottle is $60 for a good size bottle on Amazon. HK Armory brand, 62ci volume. 3000 psi.
It does cost money to fill up that supply bottle (the big thing that then feeds the regulator, which feeds the blaster). For me it's usually like $5 or $10 to get it filled at a local scuba shop. You can also buy at home HPA air compressors. ~$300 for a meh one on Amazon, $1000+ for better ones. I'd say it's best to just fill them locally.
The pneumatic cylinder was like $10 each on AliExpress. Single acting piston. "CDJ2B10-75S pneumatic cylinder".
The solenoid valve was $16 on Amazon. "TAILONZ PNEUMATIC 1/8"NPT Solenoid Valve 3V110-06 DC12V Single Coil Pilot-Operated Electric 2 Position 3 Way Connection Type (Outlet wire)" https://www.amazon.com/dp/B0BWDSJCCS
The Roboman automation HPA Core (Cosmic Nomad is the name of it) is $50 on his website. A new batch of them will probably be made within the next few months. https://roboman.net/products/cosmic-nomad-hpa-dump-tank
Then you add filament, wire, the trigger switch, XT60 connectors, screws, the barrel, etc etc etc. (~$35 iirc).
I think just the stuff actually on the blaster (so no regulator and no supply tank) is like $115 for the whole thing (hardware + filament cost).
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
Full hardware list (parts list, bill of materials, whatever you want to call it): https://docs.google.com/spreadsheets/d/17lLCGpWaN8VrMLZ8hM6eC0Pbah_-sVxC1qZsMWaTdZw/edit?gid=795135172#gid=795135172
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
The battery for the blaster and the air tank and the regulator are all intended to be held in a backpack or hip holster of some type, with the wires and air line running into the back of the grip (I bundle them together using cable routing sheathes, but you could use tape or zip ties ezpz).
Right now, I have it so the trigger wires and the solenoid valve wires each come out of the back of the grip, and then I have two xt-30 connectors which connect them to the correct spots on the electronics box stuff, which lives in the backpack/holster with the air supply tank stuff.
This is the wiring diagram for the blaster and the Xiao RP2040 microcontroller that controls the firing:
For a full list of components, look at the hardware list here: https://docs.google.com/spreadsheets/d/17lLCGpWaN8VrMLZ8hM6eC0Pbah_-sVxC1qZsMWaTdZw/edit?gid=795135172#gid=795135172
It is also possible to wire the HPA Thing to be a "dumb" blaster with no microcontroller. That means that you'll be stuck with semi auto only (for now), and it will also be possible to pull the trigger repeatedly too fast causing the blaster to short-stroke (aka, it won't let the bolt all the way back to pick up the next dart before trying to fire again). That doesn't break stuff, it just means you need to pull the trigger without spamming it as fast as you can. Ezpz!
For that setup, just connect the battery, solenoid valve, and trigger switch in one big circle. When you pull the trigger, the solenoid valve turns off and fires a dart. When you let go of the trigger, the solenoid valve turns back on, and pressurizes the HPA core and the pneumatic cylinder which operates the ram/bolt.
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
Make sure that the -012 o-ring on the tip of the ram is lubricated well.
Also lubricate the gear that sits in the back portion of the blaster.
The barrel is held in place by an m3 screw on the bottom of the front picatinny.
Wire routing in the grip around the solenoid valve can be a bit tight. Just be careful not to cut into the wires with the grip screws, and try putting everything in there slowly and carefully to make it fit.
Make sure ALL the supports are removed from any parts with supports.
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
Code for the Xiao rp2040 is by Wonderboy. Currently there is code for semi auto (just 1 mode) and full auto/burst/semi auto (mode is switched by changing a line in the code).
In the code, you can adjust the timing (in ms) of when the blaster fires after a trigger pull, and how long the blaster waits for the bolt to cycle back before it begins repressurizing the HPA core and the pneumatic cylinder. The default timings (50ms and 200ms respectively) work well in my testing.
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
Thanks to the people who helped with the development of the HPA Thing:
Wonderboy
Roboman
DonutCat
Chance
RedCowl
filipinodannydevito
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
If you print any of my designs, I'd love to see yours! Please consider leaving a Make on the Printables page, and leaving a review!
STLs, F3D, and STEP files are all here on this Printables page. Feel free to edit the parts to improve upon the blaster!
The font for the HPA Thing logo is Lobster.
China: 你好！ 我擁有這個設計。 想生產請聯繫我. 你好！ 我拥有这个设计。 如果你想生产，请联系我.
Changelog:
8-5-2025: Beta 1 release.
1-11-2026: Uploaded the Beta 1 files to Printables (it used to be just on the Roboman Discord server).
----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
If you like what I do, please consider supporting me!
I don't charge for my files, so any donations or merch purchases would be greatly appreciated!
Patreon (Monthly donations)
Buy Me A Coffee (One-time donations)
Fourthwall (NEW!) My merch shop! Go get some cool stickers and fun shirts!
RedBubble My old merch shop. It's still there, but Fourthwall makes better stuff IMO.
License:
Creative Commons — Attribution — Noncommercial — Share Alike
Sillybutts
