these are the general plans for an air powered cannon that will launch a golfball incredible distances. If the barrel size is changed you can shoot bigger things like tennis balls.

disclaimer: I am not responsible for what you choose to do with this thing. I will say it is unwise to point it at any thing that is living as it is fairly unpredictable.

Step 1: Materials

you need:
-the best pvc glue you can find
-one and a half feet of 4" pvc pipe
-2 feet of 2" pvc pipe
-3" of 1/2" pvc pipe
-2 4" to 2" reducers
-2 2" to 1/2" reducers
-2 1/2" female adaptors
-a 1/2" metal gas valve
-a 1/2" to 1/4" metal bushing
-a pressure gauge
-an air hose quick connection
-a 2" pvc water valve
-a 2" pvc Y

Step 2: Connections

cut 2 pieces off of the 2" pipe about 2" long pipe to use to connect the water vavle and the Y to the reducers

Step 3: Fillin' Station

Attach the quick connect to the gas valve. use teflon tape or pipe dope to get a good seal. thread that into one of the reducers and that into the strait end of the Y. thread the preasure gauge into the other reducer and put that into the other branch ot the Y. using one of your 2" pieces attach the Y to one of the 2" to 4" reducers.

Step 4: The Business End

Glue the 2" pipe in one end of the water valve and glue the remaining 2" piece on the other end. on that piece glue the 2" to 4" reducer and then the 4" pipe

Step 5: IT LIVES!!!!!

Glue the two pieces together and then put extra glue on the out side of all your connections just to be sure. be sure to let it dry for a few hours. we shot ours while it was still wet and my friend almost broke his thumb when the end came off.

Step 6: Ready, Fire, Aim.

there's really no way to aim so you just gotta point and shoot. MAKE SURE to not shoot it at anyone or any thing that is alive. it will drive a golf ball through a 1/2" of sheet rock. a wash rag is needed to keep a seal around the golfball. keep in mind that a smaller barrel will shoot smaller things like marbles and a bigger barrel will shoot bigger things like tennis balls. also the glue will only hold so much pressure so I don't jack mine up past 60 to 70 psi. have fun and keep safe. as soon as I build it I'll post one about a high pressure marble cannon.