Pop / Spud / Water Gun
An easy to make, basic popgun. You can fine tune the design to make a varied ammo launcher. The same large syringe can be used to fire corks, potato pellets and streams of water.
Tie the cork to the plunger with string and the syringe turns into a traditional rapid fire pop gun.
As a water pistol it can fire up to 10 meters with some elbow grease. Dip the muzzle into a water supply and pull the handle back to suck up water into the barrel. The water stays in the barrel until the handle gets pushed. click on the link for the instructions in a pdf version Make a pop spud water gun.pdf
Pop/Spud/Water Gun Instructions
Barrel plastic tube 20mm x 300mm, lubricating oil or spray
Muzzle Adapter fizzy drink bottle top
Plunger Seal thick foam sheet, 40+mm screw, ridged
Handle strong plastic or aluminium tube or wooden dowel (able to slide inside the barrel)
Water gun water bottle lid, or bottle lid with small hole.
Spud gun wooden dowel 15mm x 20mm, brass or
aluminium tube 22mm x 5mm diameter
Pop gun bottle cork or thick foam sheet, string
Hacksaw, drill/bits, screwdriver, 80 to 200 grit sandpaper, hot air gun or other source of heat, hot glue gun or other sealer glue, foam circle cutter (made from the barrel tube), hammer, measuring tape/ruler
1 Saw barrel to a length of approximately 300mm or more.
Make the Circle Cutter
2 Sharpen the end of the 300mm barrel tube or a tube of the same diameter. Sharpen by rubbing the tube end on the sand paper like sharpening a pencil. Sand until you sharpen the tube to a cutting edge on the inside face of the tube.
3 Cut a fizzy drink screw top and one inch (2.5cm) of
bottle, from the top of a fizzy drink bottle.
Put the bottle top over a tube or some cylinder the
same size as the barrel tube. Shrink the bottle top
using a heat gun or other heat source until it is nearly
gripping the tube.
4 Put the bottle top over the end of the barrel. Glue on tightly with a circle of hot glue around the end of the barrel, making an air tight seal between the bottle and the barrel. Test air tightness by putting your palm over the muzzle adapter and blowing through the barrel. If you can blow at all you will need to block up around the back of the muzzle with more hot glue or other sealer.
Wooden Dowel Handle
5 Saw the wooden dowel to a length a hand width longer than the barrel. Make sure the saw cut is squarely across on the plunger seal end. Drill a hole directly in one end using a drill bit smaller than your screw. You can make an angled handle from a larger wooden dowel.
6 Plug the end of the tube using a 3cm long wooden dowel, hammered tightly into place.
7 Drill a hole straight into the wooden plug using a drill bit smaller than your screw.
8 Using a hammer or a heat gun, bend the other end of the handle tube to make an angled gun handle.
Note If your handle is thinner than the barrel you may want to put a bottle lid on the back end of the barrel. Drill a hole in the lid the same size as the handle. This will stop the handle from moving around sideways. It will also stop the handle from being pulled out of the barrel altogether.
9 Make two foam circles with the foam circle cutter. Twist the cutter in opposite directions while pressing the cutter down on the foam sheet.
10 Glue the two foam circles together with a small amount of hot glue. Make sure they are in perfect alignment or the plunger could leak air.
11 Cut a circle of plastic slightly smaller than the foam circle. Glue onto one end of the foam.
12 Make a hole for the screw by drilling, with a smaller drill bit, through the centre of the plastic circle and out the other end of the foam.
13 Screw the screw through the plastic circle and all the way out of the foam. Keep screwing until the head of the screw is touching the plastic circle.
14 Screw the plunger seal into the end of the handle until the handle presses against the foam circle. Test the plunger size in the barrel. If the plunger is loose inside the barrel, turn the screw in quarter turns until the plunger is pressing firmly against the inside of the barrel.
15 Test the air tightness of the plunger seal by blocking up the muzzle of the barrel with your palm and pushing the plunger inwards. If the seal is tight you should feel a build up of air pressure. Or create a vacuum by pulling the plunger outwards. If the gun is leaking air, try tightening the screw.
16 Lubricating oil or spray can be used to make the plunger slide more easily in the barrel, enabling the handle to be pushed more quickly.
17 The cork can be tied to the plunger with string. One end of the chord around the screw and the other end glued into the middle of the end of the cork. The string should be just long enough to give the plunger enough distance to fire the cork every time, for rapid POP fire
18 Screw a water bottle lid or flat lid with a small hole in it, on to the adapter. Sink muzzle of the water pistol into a container of water and pull slowly back on the handle, sucking up the water. Aim at target and push handle inwards squirting water out the muzzle lid.
19 Cut a 15mm length of wooden dowel that fits snugly into the adapter. Drill a hole through the centre of the end of the dowel.
20 Glue a 22mm long section of brass or aluminium tube into the hole with one end of the brass sticking out 6mm (spud barrel).
21 Drill a hole, the same size as the spud barrel, through the middle of the fizzy bottle lid.
22 Push the spud barrel through the hole in the fizzy lid from underneath and glue in place. Screw bottle lid onto the adapter. Pull the handle back, dig the spud barrel into a potato. Break the barrel sideways out of the potato leaving a spud bullet in the barrel. Aim at the target and push the handle inwards.
• For maximum pop gun fire power, use a cork that fits very tightly in the muzzle adapter. You need to find a balance between the pressure of the plunger seal against the inside of the barrel, and the pressure of the cork against the inside of the muzzle adapter. If the cork is jammed very tightly in the adapter, the plunger seal is more likely to
• The plunger seal can be made from any dense closed cell foam. Jandals can make good seals.
• Plumbers and electricians throw out small sections of PVC tube suitable for a barrel. Aluminium tube from old
mops and other tools can also be used. The tube needs to be straight and clean inside.