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Green Gas vs CO2 for Airsoft: Which Should You Buy?
Updated 14 September 2026 · model-based buying guide
Green gas or CO₂: which should you buy?
Start with green gas if you want refillable magazines and normally play in mild conditions. Choose a documented CO₂ model if you prefer cartridges and your field allows that exact setup. If you want both options, the SRC Glock 17 Gen 5 MOS variants below support the corresponding SRC gas and CO₂ magazines.
Buy the pistol and magazine as a matched system. A CO₂ magazine is not a general-purpose conversion for a green-gas pistol, and the gas label alone does not tell you the gun’s range, accuracy or suitability for your field.
Compact green-gas choice
Umarex (VFC) Glock 19 Gen 5 GBB Airsoft Pistol
Choose the VFC G19 Gen 5 for a compact, refillable-gas sidearm with a dedicated spare magazine available.
This recommendation is green gas only; it does not assert CO₂ compatibility.
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MOS · start with green gas
Umarex (SRC) Glock 17 Gen 5 MOS GBB Airsoft Pistol
Choose the SRC gas version when you want refillable gas now and a documented CO₂-magazine option later.
Exact model: SRC G17 Gen 5 MOS. Use the SRC magazines linked below.
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MOS · start with CO₂
Umarex (SRC) Glock 17 Gen 5 MOS CO2 Airsoft Pistol
Choose the SRC CO₂ version if cartridge use is your preferred starting setup.
Exact model: SRC G17 Gen 5 MOS. The gas-magazine alternative is sold separately.
View ProductStock checked on 14 September 2026 and may change. Open the product page for current pricing, availability and purchase options.
What changes between the two gases?
Decision
Green gas
CO₂
Supply
A refillable magazine filled from an airsoft-gas can; formulation can vary by product.
A cartridge used in a magazine or compartment designed for the specified cartridge size.
Temperature and pace
Pressure and cycling can drop as the magazine cools, including during rapid strings.
Also affected by temperature and cooling. A CO₂ label is not a guarantee of consistent cycling in the cold.
Running cost
Depends on local gas prices, magazine size, refill losses and shots per fill.
Depends on local cartridge prices and shots per cartridge. Neither is always cheaper.
Power and field use
Measured output depends on the exact gun, gas, BB weight and conditions.
The same is true for CO₂. Higher storage pressure does not automatically mean more usable range.
Maintenance
Follow the gun and magazine instructions. Gas containing lubricant does not replace maintenance.
Follow the CO₂ model’s instructions for seals, storage and cartridge handling.
Choose for your usual conditions
Mild weather, casual games and convenient refills
Start with the VFC G19 Gen 5 if compact size is the priority. Choose the SRC G17 Gen 5 MOS gas version if you also want the supplied optics plates and an explicitly supported second power option. The choice is based on these products’ configurations, not a universal performance advantage for green gas.
Cool weather or longer strings of shots
The SRC G17 Gen 5 MOS CO₂ version is a cartridge-powered option to consider, but this guide does not claim a tested minimum operating temperature. Both systems can cool down during use. If the exact pistol has no verified performance data for your conditions, do not buy it on a promise that CO₂ will solve the problem; consider electric power if avoiding gas cooldown is the main requirement.
Indoor fields or strict energy limits
Check your venue’s rules for the exact setup. The SRC product descriptions quote different example outputs for gas and CO₂, while some catalogue fields disagree; these are not acceptance guarantees. Chronograph with the BB weight, gas and temperature you will actually use. Do not choose a product solely because a listed FPS looks under a limit.
You want one platform with two fuel options
Choose one of the two SRC G17 Gen 5 MOS versions above and buy the corresponding SRC magazine for the second gas. Both exact pistol listings document this route. This does not establish compatibility with VFC, GHK or every other SRC Glock model.
Complete the model-specific purchase
Chosen pistol
Next purchase
Do not substitute
SRC or GHK Glock magazines; a CO₂ magazine without documented approval.
SRC G17 Gen 5 MOS gas version
A VFC/GHK magazine bearing the same Glock number.
SRC G17 Gen 5 MOS CO₂ version
An arbitrary cartridge size or a refill adapter not specified for the magazine.
VFC compact pairing
Umarex (VFC) 20 Rds Green Gas Magazine For Glock 19 Gen5 GBB
The dedicated spare for the VFC G19 Gen 5 green-gas recommendation.
20 rounds; the listing names G19 Gen 5 fit.
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SRC refillable-gas pairing
Umarex (SRC) 18rds Glock 17 Gen 5 Airsoft Gas Magazine
Use this gas magazine with either SRC G17 Gen 5 MOS version compared here.
18 rounds; same SRC platform, gas reservoir version.
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SRC CO₂ pairing
Umarex (SRC) 18rds Glock 17 Gen 5 Airsoft CO2 Magazine
Use this CO₂ magazine with either SRC G17 Gen 5 MOS version compared here.
18 rounds; follow its specified cartridge instructions.
View ProductFrequently asked before buying
Can I put CO₂ in any green-gas pistol?
No. Only use a power source and magazine that the exact model supports. The verified example here is the SRC G17 Gen 5 MOS family, using its corresponding SRC magazines.
Is green gas the right choice for every Tokyo Marui pistol?
No. For example, Marui’s Hi-Capa 4.3 and D.O.R. specify Marui HFC134a or Non-Freon Gun Power. Follow the model manual rather than generalising from the word “gas”.
What should I buy next?
Choose the exact pistol, then its matched spare magazine. Add the fuel specified for that magazine only after checking shipping availability for your destination. For size and budget comparisons, use the Glock buying guide or Hi-Capa buying guide.
Product-level recommendations are based on the linked eHobbyAsia pistol and magazine descriptions. No cold-weather testing or universal FPS comparison is claimed.
