The Co2 12gm Powerlets are used with Pneu-Dart Models 176B and 179B, and the X-Caliber, they are designed to permit CO2 gas to expand when exposed to the atmosphere. Clean piercing, rust resistant cartridges traditionally facilitate 5 to 20 shots per cartridge (Number of shots is dependent upon projector model that is being used and size of dart.)
The rate of expansion is directly related to ambient temperature; i.e., cooler temperatures yield slower expansion rates thereby reducing the effective muzzle velocity.
Co2 must ship by 'Ground', cannot go 'Air'