To be more exact, it's the use of the GBB technology in cold weather.
The gas that usually powers GBB is Propane-based (typically Propane with some secret additives - a bit like Coca Cola and its secret formula). Airsoft gas suppliers rarely seem to state what is in their gas, although I'm led to believe that a perfume to make the gas smell better and silicone for mag seal lubrication is often included . They refer to their products by impressive and strong sounding names like Brut and there are often marketing type claims along the lines that it's so good it will make your toast at the same time as keeping your gun as clean as a whistle.
Although it's not an exact science, once the air temperature drops below 12 Degrees Centigrade, the performance of Propane powered guns is affected, usually by an indicative drop in BB velocity (f.p.s).
There are ways to reduce the effect (e.g. keeping your mags warm in a pocket, not firing for prolonged periods etc), but generally it can be a problem.
Although apparently, it's not a new thing, I have suddenly become aware that Airsoft maker WE are offering CO2 (Carbon Dioxide) magazines with some of their GBB pistols, as an alternative to the normal Propane ones. Carbon Dioxide as an airsoft propellant is not usually affected by our UK winter temperatures, so weapon performance is unimpaired at the lower temperatures that we experience in our autumn and winter seasons.
A problem with CO2 weapons that I've experienced in the past is that the higher gas pressure tends to make the gun f.p.s a little hot (oh the irony). With many outdoor sites operating a 350 f.p.s limit and indoor sites tending to be less than that, use of CO2 powered weapons has often been restricted in the past.
It is my understanding that those lovely people at WE have got the pressure regulated to a respectable 320 f.p.s (don't take my word for it - I'm only repeating what I've been told), which would suggest that CO2 pistols could be back on the menu.
Carbon Dioxide can be provided in 12g metal bulbs for Airsoft. Where Propane is usually introduced into its magazines by squirting it in to the reservoir using an aerosol cannister, the CO2 route allows you to screw in a bulb instead. It has to be said that the magazines are very different internally, so you can't use the same magazine for both forms of propellant.
Thinking ahead to the Okto Eight Milsim game in January (usually a cold month in the UK !), I bought the optional CO2 magazine for a WE M92 pistol to try out.
You will notice that surprisingly it comes with an Allen key in its little box.
If you turn the magazine upside down, it's possible to remove the bottom plate of the mag by lifting a slider in the magazine spring channel. Once the plate slides out, the bottom of the magazine looks like the photo above. There is a hexagonal hole (designed for the mysterious Allen key - ah that's what it's for !!).
If you insert the Allen key into the hexagonal hole and rotate it anti-clockwise, it's possible to remove the circular plug from the bottom of the magazine. The plug unscrews out, leaving the bottom of the CO2 12g bulb visible. As you unscrew the plug, you might experience a hiss of gas, which I assume is unused gas leaking out from the bulb as the physical force holding it tightly against the body of the mag is slowly released ?
Anyway, once the gas has been allowed to gently escape and the pressure is equalised, the CO2 bulb can be withdrawn completely.
Here you can see the inside of the mag chamber with the CO2 bulb removed. There is a receptacle at the top. When you fit a new 12g bulb into the chamber as a refill and screw the plug back in with the Allen key, the neck of the CO2 bulb is forced on to that receptacle, puncturing its neck seal and allowing the CO2 to flow up towards the mag valve and pressurising the magazine ready for use.
The plug acts as a 12g bulb retainer. When the bottom plate is slid back on (you have to lift that slider again first), you will see a realistic magazine end plate (with no visible refill point as you would have with a Propane type mag).
The 6mm BB's load into the magazine in the usual way and the pistol operates as it does with Propane based gas.
At the time of writing, the CO2 magazine was £4 more expensive than the normal spare gas one for the same pistol (Airsoft Zone - August 2015) and it was also possible to buy a choice of mags for some of the WE Glock models as well as their M92/M9.
Its not clear yet how long these CO2 bulb refills last, in relation to normal gas refills, so operating costs based on shots used are difficult to predict at the moment. The 12g refills can cost as little as £0.40 each (UK - CO2cartridges.co.uk) depending on source and quantity.
I'm sure many of you are already aware of this and maybe even already use the CO2 variants of the WE, but on the grounds that I wasn't aware, it seems reasonable to assume that there may be other uninformed people out there............
