Despite nitrogen being a rather poor propellant gas, you'd still pay less running it as a propane/air hybrid at the same energies. Projectiles generally are quite expensive for more energetic launchers. However, take my last hybrid build: Firing $9.00, 2" diameter ball bearings at ~1700 ft/s and using an oxygen/nitrogen/propane blend (not atmospheric air), it cost roughly $1.80 per shot for propellant. Now to achieve the same performance with helium, we'd need at least 2 cubic metres, even at 2000psi. Assuming that it's being bought in the quantities readily available to individuals, that much helium costs about $50 around here. That, and you now have to contain 2000psi helium instead of 240psi air, for the same ballistic performance.The nitrogen for one of my pneumatics costs .79¢ per shot and the 1.250" ball bearing projectiles cost about $3.75 per shot.
If one happens to have access to liquid helium it's a much closer match, but to stay fair we'd also have to assume access to liquid oxygen and bulk propane tanks, at which point hybrids still win by a long shot on affordability.
Ah, but for a pneumatic you can use free fuel, the air, if you're not too lazy to use a multi-stage pump. Currently, I'm at about $0.03 per shot for ammo, ignoring build costs.
Using air limits one to subsonic muzzle speeds, thus placing it firmly at the low performance end of the spectrum, which I mentioned in the above quote.DYI wrote:Only at the *extremely* low performance end of the spectrum can pneumatics compete cost-wise with hybrids.
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