SpudFiles

Well, after some frustration with sprinkler valves, I finally just decided to put a regular ball valve on this one, and when I get one that works, il mount it on later. This is 3" chamber 2' long. and a 2.5" barrel that is about 3' long. I'm gonna paint it up soon, and I am going to pick up some 1" and some 1 1/2" piping tomorrow for some smaller projectiles.

Burned off some of the hairs on the tennis ball, put it in water, put WD 40 on the ball valve, loaded it up to about 60 psi, shot it at my 1/4" thick steel shed, and it made a fist sized dent about an inch into the steel.(That pretty good for a ball valve?) I'l get damage shots later when I get some smaller barrels to shoot some more solid projectiles. 2.5" requires some big spuds, plus I'm out of em.

EDIT: feel free to tell me how to improve on things. (besides sprinkler valves, I know that.)

Get a bigger ball valve and elbows, and make a barrel support. Great first gun anyway, good job.

What would bigger elbows help do?

They would allow air to flow more quickly, resulting in better performance. You'd also need a bigger valve if you get bigger elbows though.

Pretty good. I would follow noname's advice as well as shortening the length of pipe going up from the chamber to the ball valve. That would help with the support problem. Then just secure a block of wood in the space for support.

Bigger valve... how about going for a modded sprinkler? Cheap compared to the increased performance you will achieve. Nice work and happy blastin!

EDIT: Since you have a large chamber volume, try to make the smaller bore barrels longer in length but still have a relatively close chamber:barrel ratio. This will give you alot more accuracy and power

Very good for a first cannon.

I can only see what looks like safe pressure rated parts there, you clearly used primer (but very neatly I must add), a pretty sensible range for the pressure gauge, and well attached stuff.

The damage seems pretty good for a ball valve cannon, but I'm sure that when you get the sprinkler valve sorted, you'll be much more impressed.

I must admit that my first cannon certainly wasn't as good as this. You're certainly inline to creating some absolute monsters of cannons further down the line.