I have an Air Magnum 850 that runs on a paintball tank and is 11.5 ft /lbs. You don't need anything like 300 bar for a sub 12 air rifle. If buying a...
You can buy a bottle with a regulator dropping the High pressure to 1000psi.
Getting the bottle to fit the gas tube is the difficult bit. You need a...
CO2 the whole gun will be designed to work at much lower pressure & because of the way the different gasses act (CO2 becoming liquid under pressure)...