Make your own compressed air hand gun with a few off the shelf parts.
Over the years I've used compressed air to launch many projectiles, from paper and straw rocket launchers to acorn, airsoft, and blow dart guns. Using compressed air as a propellant works great and you can really get some distance if you can release the air quickly enough. Using a sprinkler valve is the best way to achieve this as it releases the air instantly. I first saw the idea of a sprinkler valve as an air release mechanism in Make Magazine and thought it was genius.
The way the gun works is there is a air pump that is used to fill a air chamber inside the gun. To release the air and propel the airsoft bullet, you push a switch (which acts as the trigger) which releases the air valve and expels the air instantly.
In this version I decided to reduce the air chamber which means less pumps are needed to fill the chamber. I did think that maybe this might reduce the power of the gun but it didn't make a difference all at. Now all you need to do is to pump about 6 times on the air pump to fill the chamber and your ready to shoot. I have been talking to people a lot smarter than me on how to make the gun more powerful. One of the suggestions was to reduce the piston size of the air pump which will allow you to increase the PSI. I'll have to explore this in the next build.
I'm assuming that anyone thinking of making this is a responsible and intelligent human being. This is a serious weapon and could do some real damage so please use it responsibly.
Lets get making
Step 1: Parts and Tools
PVC Pipe. 25mm = 1 inch so if you are in the US just use 1 inch equivalents. These PVC parts are very common and you will be able to buy from any hardware store anywhere. As I'm in Australia I have linked all of the PVC parts to Bunnings.
1. 25mm tube - Bunnings
2. 2 X 25mm Caps - Bunnings
3. 25mm to 20mm reducing coupling - Bunnings
4. 20mm to 20mm coupling - Bunnings
5. 15mm x 1 / 2" PVC Faucet Socket - Bunnings
6. 25mm tee - Bunnings
Barrel - Copper/brass fittings
Copper or brass tubing and wire can usually be found at your local hobby shop. If not, then you will be able to order it on eBay
1. 5/16 (8mm) Hose Barb x 1/2" inch Female Thread - Aliexpress. I couldn't find the exact size barb for the barrel so I hacked a way to use it and it worked fine. I would suggest taking the 7mm copper tubing (this is the barrel) down to your local hardware store and working out which hose barb fits best.
2. 1 x 7mm (OD) piece of tubing. Aprox 300mm length. - eBay. This is the barrel. Top ensure you have the right size ID for the barrel, it's best to take an airsoft bullet down to the hobby shop and find tubing that the bullet fits into snuggly. Although the one that I linked to will be fine.
3. 1 x 8mm piece of tubing. You'll need about 50mm
4. 1 x 9mm piece of tubing. About 50mm should do it.
1. Sprinkler valve - I used this one
3. Laser sight - eBay
4. 9v battery
5. 9v battery holder - eBay
1. Drop saw
2. PVC glue
3. Dremel (sanding drum and cutting wheel)
4. Soldering iron and solder
6. Blow torch
Step 2: Adding the Pump to the PVC Tube
In other versions that I have made, the pump always stuck out of the end of the gun. This time I wanted to conceal the pump within the gun. To do this I had to seal the pump inside the air chamber. The pump is smaller in diameter than the 25mm PVC tube (and too big for 20mm tube) so you have to do some modifications to the tube to ensure the pump forms an air tight seal in the air chamber.
1. If you put the pump inside the PVC you will see that the top section of the pump is slightly too big to push the pump all the way through. This is a good thing as you will be modifying the tube to allow the pump to slot into the PVC. Cut a piece of tube slighly longer than the pump.
2. With a dremel (sanding drum attached) remove some of the plastic in the inside of the tube. You only want to go about 10mm deep and remove just enough so the pumps end fits inside the tube
3. Next to help secure the pump a little better (it's quite loose inside the pipe) I added some 20mm PVC tubing around the pump. With a cutting wheel on the dremel, cut down the middle. Next cut a couple of pieces off the tube and place them around the pump
4. To secure the pump into place add a good amount of PVC glue to the pump body and slide into the 25mm tubing. also add a good amount to the top of the top of the pump as well and push into place. Leave to dry for a few hours
Step 3: Modifying the Tee PVC Section
You will also need to modify the Tee to allow the 25mm tube and pump to be pushed right through. Remember, the tube and pump forms part of your air chamber so it needs to be air tight. That's why you need to push it right through the Tee
1. Grab you dremel (with the sanding drum attachment) and start to remove the plastic from the inside. You want to remove the plastic around the middle section of the Tee.
2. Keep on trying to push through the tube with the pump in it. If it doesn't fit, keep on removing material until it does. You want it to be a tight fit so don't remove too much though.
3. Once you have made the Tee wide enough for the tube to fit through, you're ready to move onto the electronics. Remove the tube from the Tee though for the minute as it's easier to put the electronics in without it in place.
Step 4: Adding the Switch and Battery Terminal
It's best to add the switch and wiring to the Tee now as it is harder to do once the air chamber is in place. I have also added a wiring schematic to help show you how it's wired up.
1. Cut a piece of the 25mm PVC pipe for the handle. It's up to you how long you want to make the handle. Just remember, it needs to be long enough to fit the battery and wires into. Plus it should be comfortable to hold in your hand.
2. Place the PVC into the bottom of the Tee. Don't glue yet as it's best to add the switch first. Mark where you want to have the switch and drill a hole for it to fit in. Also drill a smaller hole to the side which is where the wires for the sprinkler valve to go through.
3. Now it's time to solder all the circuit. just follow the diagram below and you will be fine. Remember to add extra long wires that will be attached to the sprinkler valve later on in the build.
4. Once the wiring is done, screw the switch into place in the PVC pipe and glue it into the bottom of the Tee.
5. To hold the battery in place, just add a 25mm cap to the bottom of the handle. It will hold in place so no need to do anything else.
Step 5: Adding a PVC Cap to the Pump Section
Adding a cap will help secure the pump in place and will ensure that the pump can't shoot out of the end if the glue doesn't hold.
1. Unscrew the handle section of the pump.
2. Drill a hole into the top of the cap the same size as the pump red section.
3. Add some pipe glue to the inside of the cap and place it over the rod and onto the back of the 25mm PVC tubing
4. Screw the handle back into place
Step 6: Adding the Tee to the Air Chamber Section
You are now ready to add the Tee (gun handle) to the tube and pump (air chamber).
1. As you have already modified the Tee you should be able to just push the air chamber though the Tee. You want to have the Tee at the back end of the air chamber so push the air chamber right up to where the handle of the pump is. You can always move the Tee later if you want to as long as you don’t have to glue it into place.
2. If it isn’t a tight fit, add a little PVC glue to secure into place. It will mean you won’t be able to move it so make sure you are happy with the position.
Step 7: Completing the Air Chamber
To complete the last part or the air chamber, you will need to add a few more PVC parts.
1. At this stage it’s a good idea to decide whether you can trim down the air chamber with the pump inside. The pump nozzle should be pretty much flush with the end of the PVC pipe, if not; you can trim off the excess with a drop saw.
2. Next it’s time to make the section that will screw onto the sprinkler valve. First, add the 25mm to 20mm coupling to the end of the air chamber and glue into place
3. Next, glue the 20mm to 20mm coupling into the end of the 25mm to 20mm coupling
4. Glue the 15mm x 1 / 2" PVC Faucet Socket into the 20mm coupling
5. Lastly, screw the sprinkler valve into place. Add some plumbers tape first to the end to ensure no air leaks
6. Leave to dry for a few hours before do any testing and filling the air chamber with air. It will be tempting but try and hold off.
Step 8: Soldering the Wires to the Sprinker Valve
1. First you need to add some cable ties to secure the wires to the body of the gun.
2. Next, trim the wires so they are just long enough to touch the solder points on the sprinkler valve
3. Solder the wires into place. you don't have to worry about polarities.
4. Lastly, test by attaching the battery and pushing the switch. You should hear a clicking sound in the valve which means the solenoid is opening and closing.
Step 9: Making the Barrel
To make the barrel you need to ensure that you have a piece of brass tube that an airsoft pallet. The best way to find the ideal tube is to take a few airsoft pallets down to your local hobby shop and find a brass tube that the pallets just fit down. The size that I used was 7mm OD so the ID was about 6.6mm which is perfect for a airsoft pallet to fit into. I have included a link to eBay on where you can buy this tube from if you don’t have a hobby shop nearby.
As the barrel ID was smaller than the hose barb (this screws onto the sprinkler valve), you have to add a couple of larger pieces of copper tube to ensure the barrel fits correctly.
1. First you need to cut a 20mm piece of 8mm tube. This will slip over the 7mm tube and will be soldered into place later.
2. Next cut a 50mm piece of 9mm tube. This will slip onto the barb (which is 8mm) and then you can put the 8mm piece and barrel into the end of the 9mm piece.
3. Once you are happy with how it fits together, next you have to solder everything into place.
4. Add some flux to the parts and with a blow torch heat-up the parts and add solder to the joints.
5. Leave to cool and clean away any burnt flux etc ready for painting
6. Screw the barrel onto the end of the gun and decide whether you want to shorten the barrel or not. This part is completely up to you. I took about 50mm off the end of mine. Make sure that you remove any burrs etc from the end of the barrel.
Step 10: Painting
It’s up to you what colour you want to paint your gun. I went with a matte black as it dries fast and is a great looking gun colour.
1. Hang the body of the gun up and give it a few coats with the spray can.
2. Leave to dry for a good 12-24 hours. It can look dry but I find that if you don’t leave it for some time, it can pick up grease etc from your hands.
3. Next do the same thing for the barrel
Step 11: Putting Together and Using Your Gun
So now it’s time to put everything together and test out how it fires.
1. Screw the barrel into the main body of the gun
2. Add a battery to the battery terminal and push the cap back onto the handle to secure into place
3. Start to pump some air into the air chamber. If you hear any air leaks, try and identify where they are coming from. If it is coming from an area that has been glued, then I’m afraid you will need to probably do the air chamber section again. If you don’t hear anything, then you have sealed up the chamber correctly. Keep on pumping until there is a lot of pressure being pushed back onto the pump handle.
4. Next, load an airsoft pallet into the end of the barrel. On my last build I made a section in the barrel where you could load the airsoft pallet into the barrel. If you want to make this then go to step 7 in this ible' to see how I did it. As I had shortened the barrel, I didn’t think it was necessary to do this step.
5. Aim and fire. If everything goes well the pallet should shoot out the end with some serious speed. Do a whole bunch of tests - You won’t be able to help yourself.
6. The next thing to do is to add a laser sight to the gun so its accurate.
Step 12: Adding a Laser Sight
There are a lot of different sights that you can buy to add to your gun. On my last build I added a holographic sight which although I think better, was very hard to attach to the gun without it moving. You really don’t want to sight to move once it has been dialed in. Using the laser sight meant that I could clamp it to the body of the gun and lock it into place.
1. Attach the bottom clamp section of the laser sight to the body of the gun. I did this in pretty much the only place you can do it, right at the front of the gun near the barrel. You may need to use longer bolts as I found the ones supplied didn’t quite do the job.
2. Next, put the laser sight into the top clamp section and do up the bolts until the laser sight is firmly attached to the gun.
3. To dial in the sight, there are 2 small hex nuts in the sight which can be adjusted. Set-up an A4 paper target and stand about 20-30 meters away from it. Load up the gun and use the laser to aim in the middle of the target. Fire and see where it hits. Carefully adjust the laser sight until you have dialed it in.
4. That’s pretty much it. You should now have an accurate, working airsoft gun that has some serious fire power.
Remember to be responsible and don’t shoot any of the neighbours kids.