If you're going to work on anything to handle air pressures then use items designed for paintball and the correct tolerances.
Most of what you would need are available from Palmer Pursuits in the US, some items are available in the UK.
The air pressures you will experience vary. A cylinders regulated output could be 400 - 850psi, more commonly 600 - 850psi
You can check the cylinder output by attaching a regulator tester, a remote line with a gauge or the fill adaptor from a remote line with the line removed and replaced by a gauge