This small air carbine that I recently made is a great backyard toy/weapon because of the fact that you can shoot anything that fits into the barrel. The design that I have made is very versatile because you can make it in any size of PVC you want. This carbine is made with 3/4 inch PVC, I think that is is the best size because you can shoot paintballs, marbles, ball bearings, and many other great projectiles.
Take the PVC Cap and put it in a vice if you have one, if not set it on a block of scrap wood. Then get you valve and drill. MAKE SURE YOU DRILL BIT IS THE SAME SIZE OR SMALLER THAN YOUR PVC VALVE! Drill a hole in the center of the PVC cap. Take your valve and make sure it can fit in the hole. Cover the hole at bottom of the valve with a small piece of painters tape so PVC glue doesn't get in you valve. Put PVC glue on the valve and in the hole in the PVC cap, then slide the valve in the hole in the cap. Let it dry.
Take your 2'- 4' Piece of PVC and glue it into you PVC Valve. This will be your barrel and trigger.
Take the PVC Valve you just glued to the barrel and the 4" Piece of PVC and Glue them together.
Take the trigger piece you just glued, and glue it to one of your 120° elbows. (IMPORTANT!) If you are right handed then put the valve handle on the left side like show in the picture. If you are left handed put the valve handle on your right side.
Glue the 2" Piece of PVC to the 120° elbow you just glued. Then glue the other 120° elbow to the 2" inch piece so that is matches the picture.
Glue one of the 90° elbows to the 2" piece you just glued, then glue a 2.5" piece of PVC to the 90° elbow previously glued. Then glue the other 90° elbow onto the 2.5" piece.
Glue the 14" Piece of PVC to the 90° elbow. Then glue the end cap you glued the valve into in Step 1 to the 14" Piece of PVC. Let the carbine dry for 1-2 hours.
Step 9: Almost Done!
With an air compressor or bike pump and pump you gun up to 120psi. Listen for any air leaking out of the compressed air reservoir. If there are any leaks then cover that part with PVC glue and let it dry again for 1-2 hours. If there are no leaks then get a projectile that will fit in your carbine's barrel. Take your carbine to a safe place to shoot and aim it like a regular gun. This carbine has trigger fairly similar to a regular gun, but instead of squeezing the trigger you will have to pull it back with your finger. The trigger might be a little had to pull, but you will get used to it. If the trigger is to had for you to pull with you finger, then put some oil into it and it should loosen it up. WARNING!!! THIS IS A DANGEROUS WEAPON!!! DO NOT AIM IT OR SHOOT IT A PEOPLE!!! THIS DEVICE SHOULD ONLY BE SHOT WITH ADULT SUPER VISION AND IN A SAFE PLACE!!! ALWAYS USE EYE PROTECTION WHEN USING THIS WEAPON!!!