CO2 tanks are not to be fooled with. I used to play paint ball alot, I had one tanl that was giving my gun fits. I unscrewed it and flipped it with the valve up to look at it and determin the problem. Suddenly the burst disk and another piece of brass popped out propelling it from my hand into my foot. A short trip to the hospital later, I found out I had 4 bones in my foot broken.
According to my tanks manufacturer [brass eagle] This was most likely from overfilling at the welding store that filled my tanks, and the fact that the tank was bought 2nd hand, was several years old [9 at the time], never maintaned[wtf is this white stuff on my tank valve] and stored improperly [rattled around in my car trunk in the 3 years I had it].
This tank was only a 20 oz. I wouldnt want to see a snafu with an overpressurized 5lb tank