This is my first Instructable so please excuse me if its not the best. This Instructable will show you how to build an air gun that will shoot all kinds of things. (I know the title is homemade paintball gun but i havnt tested it with paintballs yet. I hope they dont just pop in the barrel.)Mine cost about 13$ but it may cost more or less. Plus i already had the cement and primer.

Step 1: Gather Materials

YOU WILL NEED.....
1 TIRE REPLACEMENT VALVE (THE THING YOU PUMP AIR INTO ON A TIRE)
1 1IN PVC END CAP
1 3/4IN PVC BALL VALVE
1 3/4IN PVC NIPPLE
1 1IN TO 3/4IN PVC REDUCER
2 1IN PVC TEE
2 1IN 90 DEGREE PVC ELBOWS
A LENGTH OF 1IN PVC 6 FEET SHOULD BE ENOUGH
FIGURE OUT HOW LONG YOU WANT THE BARREL...
YOU WILL NEED A PIECE OF 3/4 IN PVC THE LENGHT YOU WANT YOUR BARREL
IF ANY OF YOUR PARTS SCREW ON THEN YOU WILL ALSO NEED PLUMBERS TAPE

*MAKE SURE YOUR PVC IS PRESSURE RATED. IF IT RUPSURES YOULL PROBOBLY BE IN THE HOSPITAL HAVING PVC DUG OUT OF YOU. I AM NOT RESPONSIBLE FOR AANY DAMAGE YOU DO. THIS COULD BE VERY DANGEROUS. TREAT IT LIKE A REAL GUN.

Step 2: Build It

THE FIRST THING YOUR GOING TO DO IS CUT SOME 1IN PVC. YOU NEED TO CUT TWO IDENTICALPIECES THAT ARE ABOUT 1 FOOT LONG. (NOT EXACT BUT MAKE SURE THEY ARE EXACTLY THE SAME LENGHTH OR IT WILL BE HARD TO CONNECT LATER.

ALSO IF ANY OF YOUR PARTS ARE THREADED COVER THE THREADS WITH PLUMBERS TAPE.

Step 3: START CEMENTING

IM GOING TO TELL YOU ABOUT THE CEMENT AND PRIMER REAL QUICK. YOU BRUSH THE PRIMER ON BOTH THINGS YOU ARE CONNECTING AND THEN DO THE SAME WITH THE CEMENT. USE WAY MORE THEN YOU THINK YOULL NEED WITH BOTH. ITS ALRIGHT IF IT RUNS OUT THE SIDES.THEN JUST PUSH THEM TOGETHER AND APLLY FORCE FOR ABOUT TEN SECONDS.

NOW WE ARE GOING TO CEMENT ELBOWS TO BOTH SIDES OF ONE OF THE PIECES WE CUT IN THE PRIVIOUS STEP. THEY BOTH NEED TO BE POINTING THE SAME DIRECTION OR IT WONT FIT WHEN YOU CONNECT IT LATER. REMEMBER THEY HAVE TO BE POINTING THE SAME DIRECTION. THE PICTURE BELOW IS ONE HALF OF THE WHOLE PIECE YOU JUST MADE.

Step 4: THE OTHER PIECE

NOW YOU ARE GOING TO DO THE SAME THING TO THE OTHER PIECE BUT USING TEES THIS TIME.ONE SIDE SHOULD LOOK LIKE A "T" ON ITS SIDE. THE OTHER SHOULD LOOK DIFFRENT. I DNT KNOW HOW TO DESCRIBE IT BUT YOU SHOULD BE ABLE TO FIGURE IT OUT FROM THE PICTURE.

NOW CEMENT YOUR REDUCER INTO THE END THAT IS POINTING TO THE SIDE.

Step 5: CONNECT THE TWO

NOW YOU NEED TO CUT TWO PIECES OF 1IN PVC THAT IS ABOUT 2IN LONG. THE 2 SHOULD BE IDENTICAL. NOW CEMENT THEM INTO THE TWO ELBOWS. SOME OF IT SHOULD STILL BE STICKING OUT. NOW CONNECT THE PIECE WITH THE TEES SO THAT IT MAKES A BOX LIKE THE PICTURE BELOW.

Step 6: CONNECT THE BALL VALVE AND BARREL.

NOW SCREW THE THREADED NIPPLE INTO THEREDUCER. THEN SCREW THE BALL VALVE ONTO THE NIPPLE. THE BARREL SHOULD THEN CONNECT RIGHT ONTO THE VALVE.

Step 7: FINISHING UP

DRILL A HOLE IN THE END CAP THAT IS ABOUT THE SIZE OF YOUR TIRE VALVE. ATTATCH THE TIRE VALVE TO THE END CAP AND SEAL IT WITH SUPER GLUE.

WHILE THATS DRYING CUT A PIECE OF 1IN PVC ABOUT 3/4 OF A FOOT LONG.
CEMENT IT TO THE OPENING IN ONE OF YOUR TEES. ONCE YOUR END CAP HAS DRIED CEMENT IT TO THE END OF THE PEICE YOU JUST ATTACHED.

Step 8: FIREING INSTRUCTIONS

YOUR ALL DONE. YOU NEED TO WAIT ATLEAST 24 HOURS BEFORE FIREING. WHEN READY TO FIRE DONT PUMP IT ALL THE WAY UP TO 100 PSI (WHICH IS WERE YOU WILL FIRE IT). I WOULD RECOMEND A TEST AT 30 PSI.
WHEN PUMPING MAKE SHURE THE BALL VALVE IS SHUT AND IF THERE ARE AIR LEAKS YOU WILL HAVE TO START OVER. DONT TRY TO PATCH THEM.

NEVER SHOOT LIVING THINGS INCLUDING YOU OR YOUR FRIENDS. IF YOU DO THEY WILL PROBOBLY BE IN THE HOSPITAL FOR A LONG LONG LONG LONG TIME. REMEMBER ALWAYS TREAT IT LIKE A REAL GUN AND ALWAYS TREAT IT AS IF ITS LOADED.

HAVE FUN AND SATY SAFE.

DONT SHOOT ANYTHING YOU DONT WANT BROKEN.