In this guide
You’ve decided on a gas blowback pistol. Smart choice, there’s nothing quite like the satisfying kick of a GBB slide racking back with every shot. But now you’ve hit the first fork in the road: green gas or CO2?
It’s not just about which gas canister you buy. The gas type affects your pistol’s power, running costs, cold weather reliability, maintenance needs and even its lifespan. Choose the right one for how and where you play and your sidearm will serve you well for years. Not sure which suits how you play? Pop into our Rochester shop in Kent and our team will talk you through it. Choose wrong and you’ll spend half your game day troubleshooting.
Here’s everything you need to know, based on what we see in the shop and workshop every week.
Not sure about gas blowback vs electric? Read our AEG vs GBB vs HPA comparison first.
The basics: what’s the difference?
Green gas
Green gas is essentially propane with a small amount of silicone lubricant mixed in. It comes in pressurised cans (usually 300ml or 600ml) and you fill your magazine by pressing the can’s nozzle against the magazine’s fill valve. The gas both propels the BB and cycles the slide.
- Pressure: ~145 PSI at 20°C
- FPS range: 280–330 FPS (0.20g BB, depending on gun)
- Cost per can: £10–£15 for 600ml
- Shots per fill: 1.5–2 magazines per fill (roughly 30–50 shots)
CO2
CO2 comes in small 12g disposable cartridges (the same ones used in some beer dispensers and air rifles). The cartridge slots into the base of the magazine and is punctured by a screw-top seal. CO2 has significantly higher pressure than green gas.
- Pressure: ~850 PSI at 20°C
- FPS range: 300–400+ FPS (0.20g BB, often too hot for UK sites)
- Cost per cartridge: £0.50–£1.00 each
- Shots per cartridge: 40–60 shots
Head-to-head comparison
| Factor | Green Gas | CO2 | Winner |
|---|---|---|---|
| Power/FPS | 280–330 FPS | 300–400+ FPS | CO2 (but often too hot) |
| Blowback kick | Moderate | Strong | CO2 |
| Cold weather | Poor below 10°C | Good down to ~5°C | CO2 |
| Cost per shot | ~0.5p | ~1.5p | Green gas |
| Magazine refill speed | 5 seconds | 30 seconds (cartridge swap) | Green gas |
| Maintenance needs | Low (built-in silicone) | Higher (needs external lubing) | Green gas |
| Gun wear | Gentle on internals | Harder on seals and slides | Green gas |
| UK site compliance | Usually within limits | Often shoots hot | Green gas |
| Realism (kick/sound) | Good | Excellent | CO2 |
When to choose green gas
Green gas is the better choice for most UK airsoft players and here’s why:
UK FPS limits matter
Most UK airsoft sites set pistol limits between 300–350 FPS on 0.20g BBs. Green gas pistols typically sit comfortably within this range without modification. CO2 pistols frequently shoot over 350 FPS out of the box, meaning they fail chrono and you can’t use them until you’ve fitted a lower-power valve or NPAS (Nozzle Power Adjustment System).
We chrono every pistol that leaves our shop and we can tell you, CO2 pistols fail more often than they pass at UK site limits.
Lower running costs
A 600ml can of green gas costs around £12 and will fill your magazine approximately 30–40 times. At two fills per game day, that’s 15–20 game days per can. CO2 cartridges cost less individually (50p–£1 each) but you’ll use 2–3 per game day. Over a season, green gas works out roughly 30% cheaper.
Built-in lubrication
Green gas contains silicone oil that lubricates your magazine’s O-rings and internal seals every time you refill. This means less maintenance and longer seal life. CO2 is dry, it contains no lubricant so you need to manually oil your magazine seals every few uses to prevent them drying out and leaking.
Gentler on your gun
The lower pressure of green gas puts less stress on your pistol’s slide, frame and internal components. This translates to a longer lifespan, especially for polymer-framed pistols. CO2’s higher pressure can crack slides on budget guns and wears down nozzle return springs faster.
Best green gas pistols
- Tokyo Marui Hi-Capa 5.1, the gold standard
- Tokyo Marui G17 and G19, reliable and accurate
- ASG CZ P-09, excellent value
- WE Tech G-series pistols, budget-friendly
When to choose CO2
CO2 has genuine advantages in specific situations:
Winter airsoft
This is CO2’s biggest selling point. Green gas is essentially propane and propane loses pressure rapidly below about 10°C. On a cold January morning in Kent, your green gas pistol might give you three sluggish shots before the magazine can’t cycle the slide any more. CO2 maintains consistent pressure down to around 5°C, making it far more reliable in cold conditions.
If you play through winter, CO2 is worth considering seriously. The performance difference in cold weather is dramatic.
Realism and feedback
CO2’s higher pressure creates a noticeably stronger blowback kick and a louder report. If you value the tactile experience of shooting, the sharp snap of the slide, the punch in your hand, CO2 delivers it in a way green gas can’t match. This matters to milsim players and anyone who enjoys the mechanical feedback of a gas blowback.
Convenience for occasional use
If you only use your pistol as a backup and don’t want to worry about magazine maintenance, CO2 cartridges have one advantage: they don’t leak. A green gas magazine left filled for weeks can slowly lose gas through the seals. A sealed CO2 cartridge holds its charge indefinitely. Pop one in at the start of game day and you’re ready.
Best CO2 pistols
- ASG CZ Shadow 2, outstanding build quality
- Umarex G17 Gen5, officially licensed and CO2-powered
- KWC 1911, classic design, reliable
- Elite Force H8R, revolver, simple and fun
The NPAS solution, best of both worlds?
Some gas blowback pistols accept an NPAS (Nozzle Power Adjustment System) or equivalent adjustable valve. This lets you dial down CO2 power to meet UK FPS limits while keeping the stronger blowback and cold weather performance.
Brands like WE Tech and some KJW models are NPAS-compatible. A good tech can fit one in about 20 minutes or bring it into our workshop and we’ll sort it.
The downside: It adds £15–25 to the cost and slightly reduces the gas efficiency per cartridge.
Storage and safety
Green gas safety
- Store upright in a cool, dry place away from heat and direct sunlight
- The gas is flammable, keep away from open flames
- Fill magazines in a well-ventilated area
- Don’t overfill, listen for the hissing to stop, then give it one more short burst
CO2 safety
- Never puncture a cartridge outside of a magazine
- Don’t leave a half-used cartridge in the magazine for extended periods, it can corrode the seal
- Dispose of used cartridges in normal recycling (they’re steel)
- Store unused cartridges away from heat
Frequently asked questions
Can I use CO2 in a green gas gun?
No. Green gas and CO2 magazines are completely different designs. CO2’s pressure (850 PSI vs 145 PSI) would destroy a green gas magazine and likely damage the gun. Always use the gas type your gun and magazine are designed for.
Does green gas smell?
Slightly. Green gas is propane-based so it has a faint gas smell during filling. It dissipates quickly and isn’t noticeable during play. Some brands add scents (like “neon red” gas with a fruity smell) which is a marketing gimmick more than anything useful.
How long does a green gas can last?
A standard 600ml can provides approximately 30–40 magazine fills, depending on magazine size and temperature. For a typical game day using 2–3 fills, one can lasts most of a month of weekend play.
Is propane the same as green gas?
Essentially yes. Green gas is propane with silicone lubricant added. Some players use camping propane with a separate adapter and add silicone oil manually, it’s cheaper but messier. We’d recommend just using purpose-made green gas for convenience.
Which is better for a first pistol?
Green gas, without question. Lower running costs, easier maintenance and UK site compliance out of the box. Save CO2 for your second pistol or for winter use.
Our recommendation
For most UK airsoft players, green gas is the better choice. It’s cheaper to run, gentler on your gun, easier to maintain and more likely to pass chrono at UK sites without modification.
Choose CO2 if: you play regularly in winter, you value strong blowback realism or you have a specific CO2 pistol you love and you’re willing to fit an NPAS to manage the power.
The smart move? Own one of each. A green gas pistol for spring/summer play and a CO2 backup for the cold months. Your magazine collection might grumble at you but your game-day reliability will thank you.
Browse our BBs, gas and batteries range for Nuprol green gas, CO2 cartridges and everything you need to keep your sidearm fed. Or pop into the Rochester shop, we always have gas in stock.
