Propane / Red Gas

Because green gas is essentially propane with added lubricant, some players decant plain propane from camping or "duster" canisters into their magazines to get a higher-pressure shot — sometimes nicknamed red gas informally — for more FPS or better cycling in cold weather.

The catch is that without green gas's mixed-in silicone, magazine seals dry out and wear faster over time, and using unregulated propane can push a magazine's actual output above what a field's chrono limit or the gun's own tolerances allow. Most manufacturers explicitly warn against it for exactly that reason.

Fields that chrono strictly at the start of the day sometimes re-check power later if a gun's performance looks unusually strong, which is exactly the situation an undocumented propane fill can create without the player intending anything unsafe.