[DeathMagnetic]

I have been building air cannons for the past few years and I've never had any PVC component explode (tons of leaks but never anything exploding) so I think you guys will be safe as long as you are under the rated psi. I usually run whatever is in my compressor's tank (nothing over 120psi) and if you care I can tell you the parts I use for mine.

A few months ago I tried the water balloon idea and I found that the overall force produced by the air hitting the balloon directly would cause it to explode in the barrel. I'm not sure if you are using a type of wadding to get around this but thats the main problem I faced. My projectiles now are usually the potato whenever available after dinner and foam inserts.

Lubrication wise.. I've noticed on a few projects where I've built my own multistage cylinders that PVC and oil do not get along. This is in the sense that if you have a tight fitting component against PVC and you add oil it actually makes it harder to move. The one lubricant that seemed to work was a white lithium grease.

As far as the opportune angle for the most distance I'd say run a regulator to make sure that the psi is constant and instead of a balloon shoot something where the weight is consistent like anything you can shoot more then once obviously. Whenever you fire it mark a flag where it lands and either increase or decrease the angle depending on what you are doing.

If you any questions feel free to ask.