Airgun With EXplosive Air-Release Valve




About: I make stuff!
Forget amateurish sprinkler valves. Look no further than this type of valve for making airguns or anything where you need the air released explosively. This is my own design inspired by the valve inside an airbrush.

This instructable shows you how to make what I call the XRV (explosive release valve), which can be attached to a bicycle pump. This in turn allows you to turn an ordinary blowgun or pea-shooter into something a bit more serious.

The video does a lot of explaining, but for more detail including how it works, see the next steps.

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Materials and Tools

To make the XRV, you need a handful of easy-to-find components:


1. Flexible bike pump hose - comes with most bicycle pumps)
2. Brass or aluminium tubing (about 1-2mm) - available from hobby stores
3. O-Rings (tiny) - available from hardware stores
4. Small spring - also from hardware stores
5. Tiny screw that fits into the end of the 1-2mm tubing
6. Tiny nut or washer that fits onto the brass tubing (see video)


1. Hand drill & very small drill bit
2. Fine file
3. Blade
4. Precision screwdriver
5. Pliers or multi-grips (pictured)
6. Hand clamp
7. Superglue

Step 2: The Valve Housing

We need the valve to attach conveniently to any bicycle pump, so cut the MALE connector out of your bike pump's flexible hose.

Step 3: The Valve Shaft

Now you need to find a piece of brass or aluminium tubing that fits nicely inside the housing. It is absolutely necessary that this tube slides freely through the housing, while being a snug fit.

Step 4: Valve Air Flow

Air will explode through this small tube, but we need to drill tiny holes to allow this to happen.
With a tiny drill bit, carefully drill two or three small holes into the shaft.
File any rough edges smooth so the tube glides through the housing without sticking at all.

Step 5: Plugging Up the Shaft

The end of the shaft must be blocked off, so that the only escape for the air is through the tiny holes we've just drilled.

I found that a tiny screw works best, so you'll need to hunt for the perfect screw. The head of the screw MUST be very slightly larger than the shaft itself. The screw must also be very short (we don't want to obstruct the holes). I found the perfect screw inside a dead clock-radio - - old electronic components are a great source of tiny screws!

Drop a bit of super glue onto the screw and turn it in to the end of the tube. If the screw is a bit too small for the tube, you could very carefully crimp the tube a bit with pliers. Then the screw should be a tighter fit.

Step 6: Add a Nut to the Shaft

A nut, washer or bush of some kind needs to be added to the shaft, so find something that fits and glue it about halfway along. Once the glue has dried, this valve will be difficult to disassemble, so be sure everything's in place before you apply the glue.

Step 7: Important! Allow the Glue to Dry

Allowing the glue to dry deserves its own step because in the next step we're going to add a spring that holds the valve closed. If your glue isn't dry when you add the spring, then you'll glue the valve shut!

Go have a coffee or climb a tree. When you get back and the glue's dry, scrape off any excess with a blade. Again, this valve shaft must be very smooth and glide through the housing without any sticking or catching.

Step 8: Spring Loading

See the distance between the housing and the nut? You need to find a spring that's about 1.5 times as long. This will ensure that the spring is always holding the valve shut.

If your spring is a little too short, you can always stretch it a little (that's why mine looks a little irregular in the image).

To how to turn the spring onto the shaft, look at the video in the Intro of this instructable.

Step 9: Seal It Off

The final step is to make the valve air tight. To do this, you'll need a very small O-Ring.
Now you can see why the head of the screw needed to be larger than the shaft. The head of the screw stops the O-Ring from slipping off.

And with that, the XRV is complete!

The spring is always holding the valve closed so air will not escape.
You can test this with your mouth. Seal your lips around the housing of the valve and blow.. build up a little air pressure in your cheeks then pull the washer/nut backwards (don't push it down your throat!) The air should escape through the tube.

Note: if air is leaking through the valve, then it could be that your O-Ring isn't sealing it too well. Try adding a second O-Ring.

Step 10: How It Works

The spring constantly keeps the valve shut.
When the valve is shut, the O-Ring seals off any escape.
Air cannot escape unless the O-Ring fails.

Pulling back on the nut (green arrow) opens the valve by exposing the holes in the shaft.
Once the holes are exposed, the compressed air explodes through the shaft.

Step 11: Attaching to a Bicycle Pump

As we made the XRV from a male connector, it will attach perfectly to any bicycle pump.

You will however, need a bicycle pump that doesn't allow air to go backwards. In other words, it needs to have its own built-in one-way valve. If you don't have this, you won't be able to compress more than one plunge of the pump.

Many pumps (bicycle pumps, sports ball pumps) come fitted with a one-way valve, but the 'BBB Airshock' pump that I use has a one-way valve PLUS a reinforced hose. When the end of this hose is blocked (with my XRV), it acts as a small air tank. Air will be compressed in that tiny space and will only be released when I open the XRV.

Opening the XRV into any type of blowgun (simple pea-shooter or deadly ninja blowgun) is the aim of the whole exercise :D

The Instructables Book Contest

First Prize in the
The Instructables Book Contest

2 People Made This Project!


  • Skateboard Contest

    Skateboard Contest
  • Make it Move

    Make it Move
  • Teacher Contest

    Teacher Contest

260 Discussions


6 years ago on Introduction

The completed project. 5/32 tubing, JAMEC style quick release male connector with a 5/32 hole in the middle and suitably sized everything else. For the people who want a little more top end in their project. Good for 4mm BBs


3 months ago

wow. This has the exact same idea as a mechanism I thought of but much much more well made! Great job!


4 years ago

i tested it using my compressor and needless to say the compressor could not create enough pressure to make the valve fail, got it to 250psi and hoping it will go to at least 600psi haha

2 replies

Reply 4 years ago

haha wow. At what pressure does it become too difficult to pull the valve in? I started designing a trigger system that uses a tubular hammer to hit the valve and release the air but never got around to building it. With something like that, you'd be able to get multiple shots from a single tank.


Reply 3 years ago

Im making some thing like this an you helped me in the good derection. A shame you never finished it. Im hoping i can make just like you inof time to finish mine.


6 years ago on Step 10

I slightly messed up by screwing an ever-so-slightly larger nut into the end. I mean, it will still lock in but the clearance between the housing I'm using and the tube is already very slight. On the plus side it doesn't need super glue, but it will mean it needs some wet/dry on the outside to fix the clearance or a simple trigger to push it back into it's spot after firing.


6 years ago on Introduction

Go to any good hobby store and they will have the small tubes. Brass, copper, aluminium. 1, 2, 3, 4, 5, 6, 7mm brass, equal for the others. 305mm lengths, but they sell imperial sizes(1/16th, 1/8th, etc). Depends what you want I guess. If you want to experiment with the same size, just buy a 1m/36" length of the tube and have at it.

I ended up with 5mm(4.97~4.99mm) because darts like the extra air, however the connections to the air supply will be the hard bit. I managed to find a strong spring and the right sized screw in my box of bits, so now making a housing will be tricky. If you order something, make sure it is slightly small than required and either use a small file to make it bigger by the require amount, use some wet/dry on the shaft, or use some valve lapping compound and slide the two bits together to make the fit perfect. The better the fit, the less air escapes, and the more pressure you can put into the tube to shoot whatever you're shooting out the end.

420 O-rings on ebay of various sizes for $15.50

Anyway my thoughts on making this for a semi-auto;

1. Use thick walled tubing, you'll want to run a large amount of pressure behind the valve(3-400psi perhaps)
2. Use a strong spring. Remember, a trigger provides some mechanical advantage, so if you can barely compress the spring because of it's stiffness, then just modify the trigger to suit.
3. You need a way for the valve to release when the trigger is pulled and return whilst the trigger is still depressed, so you don't drain the reservoir or fill the barrel with BB's

Everything else will be simple enough. A paintball tank for the air, the valves/regulators will be the same as from the paintball gun, but the gun itself is expensive to import to countries like Aus(permits, fees, licences, blah blah).

Of course for a single shot this isn't a problem, just remember to take your finger off the trigger. Also be careful with paintball tanks, some are good for 5000PSI(average 3000psi), so you'll definitely need a regulator to get the right amount of pressure. Otherwise, a copper tube with ends brazed on and a schrader valve(like from a bike tyre) will probably work for a few shots so you don't have to keep pumping.

Just some thoughts

1 reply

Reply 6 years ago on Introduction

Some extra information;

I've been looking at making a slightly larger one using off the shelf parts. Anyway, I found a quick release connector(the male bit). It has threads on the inside, with a 5/32 hole in the middle. You can easily get 5/32 brass tubing, and it is a nice size to work with due to the weaknesses of tiny drill bits(plus the tollerances are tight,. The upside of using premade connectors like this is that there is usually a barb fitting with the opposite threads and it all screws together(just get some teflon tape). 10mm hose connected to a tank to hold some pressure and you're in business.

4-500psi may be safe through this depending on the wall thickness of the tubing used, the seal in the fitting and the tube, the tube construction(extruded or drawn), etc


6 years ago on Introduction

For y'all who be wondering where this guy got the little tubes, wonder no more!
Took me forever to find. Enjoy!


6 years ago on Introduction

What about water? How would this do shooting a stream of water?


8 years ago on Introduction

i machined a much larger version of this for my air rifle would anyone like to see a slideshow or ible??? credit to chluaid
of course

1 reply

Reply 7 years ago on Introduction

I'd like to see it myself I'm at
p a ll a d i n 9 8 0 0 0 at g m a i l period c o m
I'm an old dude living in Mexico building slingshots and crossbows a la J sprave for fun and profit