Add to that a used scuba tank filled at a local dive shop is much cheaper, if you don't own a compressor of your own. A good hand pump designed for air rifle use isn't all that bad if you're not shooting all the much(most hunting situations). Lawdogmjfa said:Air is mostly Nitrogen (about 79%) and N2 makes for an excellent substitute gas for air in pcp's. It has the advantages that could be get very dry and it is completely inert, without the associated humidity contents on pumped air and without the oxidation properties of O2 contents in air. It has being used by many with good success as the propellant gas in pcp's. Only drawbacks are to obtain the apropriate fittings to transfill an airgun's reservoir from an N2 tank; N2 tanks with the needed working pressure are big, heavy and expensive, although they may be rented; and that most airgun's manufacturers would void warranties if they know about the useage of nitrogen in their guns, but you don't have to tell 'em on the event of a warranty claim.