Update:what do you think of my cannon

[Charlie Brown]

I was going to-

This is a over under style pneumatic gun the tank is 6" diamitier that is 4' long and the barrel is 2" diamitier and 4 ' long. I am using a 1" sprinkler valve that i plan to mod. I will charge it to 100 psi.

Now I'm going to-

make 2 6" tanks both being 2' long and 4 1" valves

[spudshot]

that 1" valve is REALLY choking the flow, build a piston valve, or get a bigger sprinkler

[Charlie Brown]

but that a 2in valve costs like 100 bucks

[spudshot]

there are some good deals on ebay sometimes, but i'd just build a piston valve if i were you

[boilingleadbath]

Well, here's the relevent numbers:
100 psi, 100 grams, cannon dimentions as given in post unless stated otherwise.
1" sprinkler, blowgun exaust: 266 feet/sec.
2" sprinkler, blowgun exaust: 325 feet/sec.
2" sprinkler, 3/8" ball valve exaust: 429 feet/sec.
2" sprinkler, 1" spinkler exaust: 436 feet/sec.

1" ball valve, 120 ms opening: 187 feet/sec.
1.5" ball valve, 160 ms opening: 220 feet/sec.
2" ball valve, 200 ms opening: 246 feet/sec.

(with 1" spinkler, blowgun exaust)
6" chamber: 266 feet/sec.
4" chamber: 264 feet/sec.
3" chamber: 261 feet/sec.
2" chamber: 254 feet/sec.

As you can see, your 6" chamber, expensive and be heavy, barely gives any increase in preformance. The valve you use does. Also, remember that energy increases as speed*speed...

[sergeantspud2]

or what about 2 1" sprinkler valves and put them into one blow gun so they open at the same time

[boilingleadbath]

That'll give you 350 feet/sec, using dementions given in post.

But I recomend making your own valve... piston, or diaphram, preformance is about the same. Heck, make a 3" valve if you want... it won't cost much more than a 2" one.

[drac]

DUde, the valve you are using is DEFINITELY choking the flow. As others said, you should make a piston or diaphragm valve. Or, if you got about 5 valves, make a rig for em, and exhaust the together with a 6th valve.

[taterjim]

I built a cannon with a large capacity like yours and with the 1" sprinkler valve the performance was the same as another cannon I have that is only half as big. The performance is limited by the size of the valve so that all you have is more weight to pack around. I'm presently shopping for a bigger valve to give it what it needs.