How To Make A 15mm Beginner / Intermediate Pneumatic Sniper Rifle

Intro : A 15mm Beginner / Intermediate Pneumatic Sniper Rifle

New video added.
Alright... This cannon is pneumatically powered, fired by a modified 25mm Sprinkler Valve. It is a typical spud cannon that lots of people have probably seen before. The chamber acts as a stock and handle at the same time, and 1 side of binoculars for the scope.(and I find no problem with pressurizing the stock because if a chamber explodes... your stuffed whichever way you put it)

I call this gun an "Beginners'" cannon because really, a sprinkler valve is for beginners and intermediate spud gunners. Ball Valve Pneumatics are for Newbies. I don't mean that as an insult, because really, my first cannon was a ball valver. Sprinkler Valves are the "Next step up". If you are building this as your first cannon-Don't. Make a Ball Valve pneumatic or a basic combustion. They are really simple and will let you understand all that darned physics and forces etc etc unless you're alot older than me, and you already know all that stuff.
The video

It is an over-under design, by the way which means that the chamber is underneath the barrel or visa versa.

NOTE: I take no responsibility in any harm/damage/death you do with this WEAPON. This is not a little marsh mellow thing for 5 year olds that shoots 2 metres. If used dangerously or as a weapon, it could kill someone with the right ammo. Only make this if you are at least 10 years old, or if you have a good common sense.
NEW PAINTING STEP COMING SOON
This is my first instructable, and I'm only 12 years old. So don't be too harsh xDD
If you want to contact me on SpudFiles my name is Hydra

AND BEFORE YOU ASK STUPID QUESTIONS LIKE "HOW FAR DOES IT SHOOT" AND "CAN I MAKE THIS AUTOMATIC" Actually do some research first. Go on Spudfiles.com and search the forums(semi-auto, chamber-barrel ratio), Ask if you cant find anything. If you did actually do some reading around, you would know that making a semi auto gun would need a Blow forward bolt or a HEAR valve. And you would know that range depends on the angle and pressure.

First Step : What thou shalt need

Yep. What you gotta have, Of course. I have made a list of what you need.

15mm Pipe 1Metre(3ft)*# (AUS$4)
25mm Pipe 1Metre (3ft)*#(AUS$6)
2x 25mm Tee*#($2 each)
2x 25mm 90 degrees Elbow*#($1.50 ea)
2x 25mm 45 degrees Elbow*#($2-3 ea
25-15mm Threaded Reducer Bushing (1 end threaded)*(I bought a 25-20mm and a 20-15mm reducer. Both were about AUS$2-3)
2x 25mm Male-Slip Adapter (I forgot what these are called)* ($2-3)
25mm End Cap*($2-3)
25mm Orbit WaterMaster in line automatic sprinkler valve.* (Irrigation or Gardening Section)
OR A 25mm Rainbird in line automatic sprinkler valve CP-100 OR Orbit Jar Top Sprinkler Valve.($25-30)
Blow Gun Valve(?)($3-5)
Air Hose(?)($3-5 per merter)
1/4' Barbed Hose Adapter*#(same size as air hose-$1-2
Tire Valve(?)($2)
PVC Cement*#(Forgot Price
PVC Primer*#(Forgot price)
Drill*
Teflon/PTF Tape.*#(?)
Binoculars (For scope) OPTIONAL
Everything marked with a (*) you should be able to get at a HardWare Store ie (Australia) Bunnings, Mitre 10. (USA) Lowes, HomeDepot. Everything marked with a (#) You should be able to get at a Plumbing Store.
As for the (?) Marked stuff...
You should be able to get Blow Guns at places that sell Air Compressors and Air Compressor Fittings. They are used to blow little specs of dust away. Air hoses you can probably get at the same place.
Tire Valves you can get at any place that sells tires, or repairs cars. Sometimes they give it to you for free. Otherwise go to a junkyard with a knife and cut off the valve from a car tire. Binoculars are easy to find, but use an old one, not one of those obese professional binoculars that zoom 1000x, with adjustable lens.. blah blah
ALL PRICES ARE APPROXIMATE, AND AROUND THE PRICES I GOT THEM FOR. FOR YOU IT MIGHT BE CHEAPER OR MORE EXPENSIVE. DONT BLAME ME. GO SNEEZE A PILLOWCASE

NOTES:
Okay, a male pipe is a pipe that has threads on the OUTSIDE. a female pipe has threads on the INSIDE. An Elbow is simply a bend, a Tee is a bit of pipe that looks like a T. A Nipple is a short length of pipe with two male threads. A Coupling/Coupler has Female threads.
REMEMBER TO GET ALL PIPES PRESSURE RATED THIS IS SO IMPORTANT I CANT STRESS IT ENOUGH. If you get that stupid DWV Foam core stuff it will seriously stuff up your cannon...It will stuff you up even more when (not if) it explodes.

25-15mm Reducer Bushings are kind of rare where i live, it might not be where you are so yeah. Just get a normal 25-25 Bushing or maybe a 25-20mm. Then add some normal Reducer couplings. ie Bushing->Short Pipe->25-20mm Reducer->Short Pipe->20-15mm Reducer->Barrel.

Instead of getting a Hose barb and Air hose, you can attach the Blowgun Valve directly to the Sprinkler Valve with a 1/4' (6mm) Nipple.

Step 2 : Preparation

Pipe Preparation
Now you have to cut your new 25mm Pipe to shreds. Well, not really. But anyways.
Cut the pipe with a hacksaw or a PVC Saw into 8 sections.
2x 23.5cm
4x 4cm
1x 10cm
1x 15cm
1x 12cm
These aren't exact, and you will have to make a couple of adjustments, but only a cm or 2. By the way, these are the measurements i used for my gun, and my gun doesnt have a reducer bushing, but 3 reducers lined up (If you are using a 25-15mm Bushing, you only need three 4cm pieces) .
Make sure you have the most chamber volume as possible. If you have too much, you might want to make it into a silencer, but you need a huge pipe for that (minimum 30mm for a 15mm barrel)
With the end cap, drill a hole in the middle thats a bit smaller than the tire valve. Its the bit behind the massive round thing at the back. (Round thing->Largish bit->Small tube->bit where the pump connects.) Shove the small tube into the hole from the inside of the cap so the big round bit is on the inside of the cap. Take it out, slather it with epoxy and shove it back in and pull it as hard as you can.

As for the barrel, GGDT shows that for a chamber this size, the best barrel length is about 30inches (75cm) This is including the volume of the fittings...But i mainly estimated that so its probably wrong, but 20-30inches (50-75cm) is the best.
Valve Preparation
Now this is probably the hardest part of your gun, so pay attention.
!!Warning! Science Content!!! =D
Your sprinkler valve will probably come with a big black thing on top, that is the solenoid which vents the valve. The valve works with pressure differences. When the air comes into the valve, it pushes this little flexible disk (The Diaphragm) into the outlet which seals it. As more air comes inside, it goes behind the Phragm. Now either side of the Phragm is pressurised. The solenoid now vents one side of the Phragm and the pressure there is low. The high pressure on the other side pushes it back and the outlet is exposed and all the air goes through. Look at the images for more info.

Yay, physics lesson 0.o Modifying the valve replaces the solenoid with a manual blowgun valve which vents alot quicker than a Solenoid, therefore it opens faster.
I can't really explain how to modify a Sprinkler Valve, so go here. This and This will explain it alot better than I. For the second link, go to Design Library-> Orbit WaterMaster, 1" - Modification. You might want to download the thing on the first page because that really helps with designing a Pneumatic.
I modified my valve differently, by drilling a hole in the solenoid port and screwing the barb in.

Step 3 : Sprinkler Valve Modding

Just in case some people get confused by the links I gave you, I'll give you guys a description myself on how to mod a sprinkler valve)
Alright...
The first thing you do is to seal the hole in the outlet. In the outlet theres this tinylittle tube poking out. Seal that with epoxy.
Now rip the solenoid and everything off until you have a little black ring with threads which used to hold the solenoid. (The black ring screws into the Sprinkler Valve. And the solenoid (big black thingy) screws into the black ring.)
Make the hole bigger until you can ALMOST fit the hosebarb inside. The hosebarb should be able to fit if it didnt have any threads.
This bit is kinda challenging. You can either use an electric drill, some pliers or a modified circular saw. Twist the hosebarb into the hole until its in as far as it will go, then strengthen it with epoxy. You should now have a hosebarb sticking out of a sprinkler valve. Now glue the airhose to the hosebarb and glue another hosebarb to the other end. The other hosebarb screws onto a blowgun.

Step 4 : Scope

This step is optional, but if you want to make yours a sniper, go ahead and do it!
First, cut the binoculars in the red line shown in the picture. (One of the sides is broken on mine)
Make sure the focusing knob is on the side you want to work with. Alternatively, you can cut on the blue line and focus it by moving the little nub up and down. I don't recommend this because it is kinda hard to move the nub and you will be moving it too much, using the focusing knob moves it more slowly and precise.
When you turn the focusing knob, it moves a section up and down which is connected to a lens inside the binoculars, (via the nub) which is what focuses it.
If you want, you can use a spare piece of 25mm Pipe as a scope mount, cut a small section off and wrap it around the scope, glue the other side onto the gun.
When attaching your scope make sure that it is straight, like really straight, i recommend resting it on flat ground to get the right angle. When gluing the scope mount, epoxy it and place it on the ground without the scope on it so it goes on a straight angle. You might want to hot glue it so it gets held in place.
Another way to attach the scope mount is by using two pipes. Get 2 of those 25mm rings (With cut). Completely glue one on the chamber, screw the other one with the scope. Look at the last picture for details.
"on the "scope" "binocular half" you could try to draw a crosshair on the lens with a sharpie for a better aim."
Creds to letmeon for that idea.

Step 5 : Breech Loader

This step is optional, but you can make a Ball-Valve Breech Loader if you want.
Of course you can use one of those other breech loaders found on this site, but i haven't yet seen a ball valve breech loader.

It works like this. Basically theres a ball valve, and you drill a hole in the side. Now you glue it onto the barrel. Shove the ammo in the drilled-hole and twist the valve. Now theres some ammo sitting in the ball valve at the bottom of the barrel.
Obviously its not that simple.
Decide which way you want the ball valve to be facing. I made mine a 45 degree angle to the right. Like pointing from the '5' to the "9" of the number pad on your keyboard.
Mark a hole where you want to drill the hole
Now clamp it down, grab an electric drill and use a small drillbit (1/8" or 3-5mm) MAKE SURE THE BALL VALVE IS IN THE CLOSED POSITION. This is common sense but you might forget...

Now drill through the side of the ball valve with the small drill bit. This is just to make sure that you are actually in the middle of the middle of the valve. When you are done, get a pen light and look through and see if you are in the middle. If you aren't adjust it, because this will be a pilot hole for the big drillbit later on.
If you are, grab an 18mm spade drillbit and drill straight through the hole and the ball. You can drill through the other side but theres no point, because the ammo will probably fall out.
Now use the 18mm spade bit and drill through the two holes that are inline with each other, just to enlarge the ball valve because it is actually a bit smaller than the barrel.

Use sandpaper and get rid of all the dust and burr.

Step 6 : Assembly

Stock Assembly
Assemble the parts shown in the picture with PVC Cement and Primer.Here is a tutorial to glue PVC parts together.
Note: The tire valve is not shown in the picture, make sure you glue the tire valve in before PVC Cementing.

Valve+Barrel Assembly
Assemble the parts like in the picture. If you want, put some nails at the bottom of the barrel to prevent loose ammo falling in. Position the Blowgun Valve wherever you want, I put mine on the handle because its the easiest place. Its probably the same for you. Secure it there with zip ties or glue. If you have a 25mm-15mm Reducer Bushing, then screw it in the valve and glue the other end to the barrel. Nice and simple. With me, i can't get 25-15mm Bushings so i have to do this.
Valve->25mm Bushing->25mm Pipe(short)->25-20mm Reducer->20mm Pipe (Short)->20-25mm Reducer-> Barrel
You should probably zip tie the blowgun valve to the handle by the way for ease of use.

Step 7 : The worst bit.

Yep, the worst bit. Waiting for it to dry.
To have some relief from the agonizing pain, make some ammo!
AA Batteries wrapped in duct tape
Air Hose slugs*
Wooden Dowel the same length as the Air Hose slugs. (Wrapped in duct tape)
Blu-Tac wrapped in aluminum foil
Marbles wrapped in duct tape
Potato*
Apple*...All kinds of hardish food
Water
Bottles*
Pepper 'nades*
Anything you can fit in the barrel really!

• The air hose slugs are pretty cool actually. Remember when you cut your hose for the sprinkler valve modification? Well they won't go to waste. Cut it all into about 1' to 2' (25mm-50mm) sections. Then seal one end with hot glue. Wrap it in duct tape to let it fit in the barrel. I wrapped the end with the seal so I know which end to put in the barrel first. (When firing, if the heaviest bit is at the front it will allow more stability, thats why you only seal one end.)
• With potato and apple, chop it in half lengthwise and put it on the ground. Shove the barrel end into the potato all the way and bring it out. There should be a chunk of potato that fits the barrel perfectly. Push it all the way down with a stick.
• The bottle is awesome at parties and stuff, you all get wet xD! Fill the bottle halfway with water and slip the barrel into the mouth all the way into the bottom. Now fire and the bottle goes flying, but the sudden movement makes the water shoot out the back and spray everwhere. Kinda like when your in a car and suddenly you go really fast and you get shoved into your seat.

*The pepper nades were an idea from brian250. Make one of those film canister pepper bombs, shove it down the barrel SLOWLY.. And when you fire, the sudden acceleration (80Gs) will shake it up and it explodes when it lands. You can probably somehow make it out of an air hose.. because film canister are too big unless you have a different sized

Last Step : The best bit.

Now, after 24 hours of agony...It's all gonna pay off!!! =DDDD
Make sure there are no leaks. Slowly pump it up to the max pressure you are going to use it at and pour soapy water all over it. If you see any bubbles, seal the section with epoxy.
Now, load your slug first, pump it up, heft your gun to your shoulder. Spy through those lucky binoculars that got the best job in the world and...
YOUR GUN EXPLODES... Well it could happen.
Hold down the blowgun trigger quickly and WHAM! When shooting a barrel full of water, keep your feet close together and stand up straight. The recoil is like nothing... honest.

Ah well, have fun with your new contraption and please, don't shoot that granny living down the road. Sure, shoot that annoying show off toughy that everyone hates but just.. Yeah.

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