Hi! In this instructable I’ll show you how to make a little hand gun that works on flammable gas, like a potato gun. It can shoot chewed up toilet paper, plasticine, cotton swab nail darts anв steel balls for airsoft guns. This device is made of junk and can shoot right through 20 sheets of paper.
Gun has a laser sight, onboard fuel tank, a special button for laser and a trigger above it. The barrel is attached inside the combustion chamber, it makes process of reloading as fast as possible. Also there is a little magnet on the barrel for preventing a steel bullet from falling out of it. Here are some specifications: chamber volume is about 100 milliliters, barrel length is 250 millimeters with diameter 4.5 millimeters or 6 millimeters, muzzle velocity is up to 60 meters per second and muzzle energy for ВВ ball is about 0.6 joules.
For the simplest design you need a little plastic jar of vitamins, a barrel, cold weld, a piezo and some piece of wooden board to make a handle. You can find a piezo in a button lighter, just disassemble it.
Also You can watch all process of creating this gun in embedded video!
Step 1: Barrel's Fixation
Cut off about 20 centimeters of the tube to make the barrel. Its outer diameter is about 8.5 millimeters, so I drill a hole with 8 millimeters diameter for better barrel’s fixation.
Step 2: Barrel's Tune
Just insert a barrel in the combustion chamber, so that the breech will be about 20 millimeters away from the cap of the jar. Grind a barrel for best sticking with cold weld. So, stick it to the chamber with cold weld.
Note: make your finger wet for better smearing cold weld!
Step 3: Handle
Draw a handle on a piece of wooden board, then saw it with a hacksaw and work it with a file until it’s perfect.
Also make a cylindrical socket for the vitamin's jar.
Step 4: Inserting Piezo
Choose a drill to make a hole for a piezo. Limit the hole’s depth with tape, we need a piezo to stick up to the hole. Remove leftovers with a knife.
In the back end of this channel thrust in a clip, also you can use a nail for it.
Shove some foil for better electrical contact. Protect a piezo with tape and fill gaps with hot glue.
Be careful, hot glue can damage a piezo.
Step 5: Attaching the Сombustion Chamber
Mark and make holes for electrodes in the combustion chamber, then grind it for better sticking and stick it to the handle with hot glue. Also you can strengtht the chamber’s mount with some cable ties.
You can shoot right now. Remember that for shooting you need to inject a certain amount of gas into the combustion chamber. Less or more gas will make your shot weaker or just impossible.
Step 6: Upgrade Chamber's Cap
To prevent the cap from blowing out and punching you into your face, just pull it around with Cable Tie and fix it with hot glue. Now we need to seal the cap. Cut off plastic skirting and stick some piece of rubber to the cap.
Step 7: Gas Supply System
To inject gas faster you need a venous catheter.
Prepare a handle for sticking a lighter by grinding it. Slightly bend a catheter’s needle and jab it into the combustion chamber, then fix it with glue. I put the free end of pipe on the lighter’s nozzle and stick the lighter to the handle with hot glue.
Step 8: Laser Sight
Disassemble laser pointer and make a groove to reach button’s electrical contacts. Solder some wires to them and fill gaps with hot glue.
Attach a laser pointer to the barrel with cable ties and tune it like this, I can see a red dot through the barrel. And now attach laser pointer to barrel with hot glue.
Step 9: Laser's Button (tailswitch)
I use this old button (don't have another), but SMD tactile button is better. Drill a hole for a button, supply a wire and solder it. Put a button into its place and fill gaps with hot glue.
Step 10: Internal Barrel (4.5 Mm Caliber)
I decided to make an interior barrel to shoot with 4.5 mm BB airsoft balls. The balloon stick is the best barrel for 4.5 millimeters BB balls, and this stick fits perfectly in the old barrel. To prevent a steel ball from falling out of the barrel, I extracted a tiny magnet from an old CD rom. Fix it to the barrel with tape and shrinking tube. Extend the edge of a balloon’s stick to fix it into the external barrel.
Step 11: Clip
To make a clip for bullets I just glue a magnet to the combustion chamber.
Step 12: Darts
To darts them you need cotton swabs, nails and superglue. Cut a swab in a half, cut a piece of nail, smear it with superglue and insert it into a cotton swab. Done!
You can see some crazy shooting in the last part of embedded video. Also I measured bullet velocity by microphone and sound recording program, and it is about 60 m/s.
Step 13: Shooting
A potato gun (gas gun) is a very simple device. There is a mixture of fuel (propane, butane) and oxidizer (air) in the combustion chamber, which is being ignited by an electric spark, like with the engine of your car. The mixture burns out with high speed and temperature and generates pressure that forces a bullet to move through the barrel.
Remember that for shooting you need to inject a certain amount of gas into the combustion chamber. Less or more gas will make your shot weaker or just impossible.