Introduction: Simple Compressed Air Gun
This is a tutorial of how to construct a pneumatic air gun. This compressed air launcher has the ability to launch projectiles a large distance. This should be treated as a real gun, and never point it at another person, treat the gun as if it is loaded all the time. also put the projectile in the barrel before you pump the air cylinder tight just incase the valve releases or is knocked and fires the projectile.
Step 1: Cutting the Stock
firstly, the stock of the gun must be shaped and designed as to how you would like it. I have traced a marlin .22 , once the stock has been designed trace the outline onto 2 Lengths of wood at 15mm thick. or one solid piece at 30mm thick. Now that you have the outline on the wood, carefully cut on the outer side of this line with a jig saw cutter. This giving you your wooden stock.
Step 2: Compression Cylinder
Now that you have the stock it is time to construct the barrel, trigger and compression cylinder. To construct the compression cylinder I have used a 1.5L coke bottle, this bottle has whad a 19mm hole drilled in the base of it, and a 19mm clear tubing has been pushed in creating a tight fit, once the tube is in the base of the bottle I have used a hot glue gun to seal where the tube enters the hole In the base. this tube is connected to the plastic funnel shaped fitting that comes with a hand pump, yet again hot glue is used to seal this join. (also try adding cable ties around this join to give it extra strength). now that the back half of the compression cylinder is complete it is time to move onto the front half, where the bottle neck is, unscrew the cap and insert the 19mm pipe through the hole, as this is already a tight apply plumbing glue to the outer plastic tube and the inner bottle neck and firmly push the pipe into the hole.
Step 3: Trigger
now you should have a bottle connected to a pump with a piece of PVC pipe pipe coming out of the bottle neck. from here attach a screw in connector to fit the outer diameter of the pipe and the threaded side must fit into your choice of ball valve (preferably a similar sized valve), make sure you wrap Teflon tape around the thread before tighten it into the valve. so now beyond this valve it is vital that everything is air tight! by closing the valve and pumping the pump it will increase the pressure behind the valve, filling up the 1.5L coke bottle with air, this condensing it and rendering the air the propellant for the projectile. note* if you hear small leaks, try adding more hot glue.. as it melts both plastic surfaces and bonds the two materials at a molecular level.
Step 4: The Barrel
now that you have the valve that when pulled back fast releases the air, you must add another screw in joiner from the valve to join with another length of 19mm PVC pipe, from here you will not need hot glue, just plumbing glue. gluing in the PVC pipe to the connection that has been screwed into the valve will allow you to now move onto bending the pipe up through the stock and along it acting as the barrel. this will require you depending on what wood you have used for the stock to drill a 25mm hole through the back end of the wooden stock you have shaped, now glue the elbow to the pipe that is coming from the valve and let it dry. on the other end of the elbow glue another length of 19mm PVC this will be used to poke up through the stock and and out the other side, where another elbow will be glued to the pipe so it can accommodated for a barrel to run along the top of the stock.
Step 5: Finishing Up!
now that you have pretty much finished the gun, cable tie the barrel onto stock and also the pump (only if you want) onto the side of the stock so it can be easily pumped
Step 6: Firing Tips
when firing do not pump up the air cylinder to much as there is a chance the plastic will weaken and potentially explode. when finding ammo, use things that will fit tight into the barrel as it allows for a more efficient transfer of energy when firing, pull the valve down fast as it will allow the mass of air to be released at the same time rather than a little bit at a time