Well, I took the tennis ball gun out to my friend's place this afternoon, and we fired it about 30 times.
All of my previous shots were at low pressure, about 25 PSI, with compressed air.
Today, I was using CO2, from a 20 LB cylinder, at about 75 PSI.
I've got a 150 PSI regulator on the cylinder, and used a 25 FT hose. The "air" coming out of the regulator is COLD. Very, very cold. That's partly why I used a long hose, to give it a chance to not be quite as cold when it went into my PVC chamber. That seemed to work O.K.
There was frost on the fitting at the regulator, but the tire chuck at the other end never got uncomfortably cold. Of course there was a couple minutes between shots, so that had to help.
We were firing on a mowed area, about 100 yds long. Beyond that was a pasture of tall grass that would have made it impossible to find the tennis balls.
Most of our shots were fired at a very high angle, ending up about 75 yds out. I don't know how high they went, but they were way up there. 8)
It was a lot of fun, and no tennis balls were injured, or lost.
I tried catching a couple shots on my phone's video camera, with dismal results.
Let's face it, I am not Steven Spielberg.
For a maiden voyage, I'm happy with it.
Duane