The barrel, but once the chamber is filled the valve seals.

It only leaks when I hook it up to the air compressor.

Oh, one more question, the FAQ said: P: Your valve won't seal while you're pressurizing the cannon. A: You may have an equilization hole that is too small. You may also have a leak in the top of the valve, so the valve is constantly being piloted. You can expand the equilization hole with a needle o...

Ah thanks, I'll try that.

Theres a picture of the valve.

Edit: Could I fill up one of the holes where the solenoid used to be widen the other one, and just put the hose barb there?

I'm not completely sure I can tap it somewhere that doesn't interfere with the guide rod though. The valve is kind of small.

The troubleshooting guide said: P: Your sprinkler valve has a guide rod and you don't know where to mod it from. A: You can usually put the brass fitting into the valve next to the guide rod. A few members have modified the valve where the guide rod is, and have bent the guide rod so the diaphragm d...

Well, I just made a vortex block out of bondo. Took me 6 tries. I suck.

Heres a picture of it, my camera sucks at taking pictures that are close to it.

So Bondo isn't a very good material for a vortex block is it.

So the block would wear down after 10k rounds? Well thats depressing.

One more question, how long would a vortex block made out of bondo last?

Oh, ok thank you for the help. I guess I will use 1" pipe since I accidentally bought it last time I was at Home Depot. >_<

Edit: One more question, does adding the metal skirt thing make alot of a difference in firing?

Edit: Nevermind, I found the answer.

Just wondering, what is the smallest size pipe a vortex block can be put into?