So... You've got your AEG, you've had a few games and you want something different/want a sidearm? Welcome to Gas Blow Back!
There are a couple of main types of GBB airsoft guns, you've got pistols, rifles & SMGs... 90% of the time if you see a player with a pistol strapped to them in game it will be a GBB, they're fun, the top slides cycle fast giving you the illusion of recoil (kick) and you can 'almost' treat them like you would a real steel pistol! Then we come across GBB rifles, again great fun, will kick you in the shoulder everytime you fire, can be phenomenally accurate when set up well, great fun but there are some down sides... Then you get SMGs, but these are almost a cross between the two types, you tend to get larger magazine capacities & faster rates of fire in much smaller packages, as the SMGs are much smaller the felt recoil can seem larger too!
The down sides of Gas? Temperature, temperature, temperature, it's all down to how warm or cold it is, 15-20+ degrees out side? You shouldn't have a problem, snowing? Yeah, you'll run into problems! These run from a gas power source that's stored as a liquid, but the guns are powered by the gas after it has evaporated. The process of evaporation is endothermic which means as the liquid tuns into gas it sucks the heat from everything around it which is why your magazines cool down as you fire. As everything gets cooler the whole lot gets less efficient, meaning more gas is used, the colder it gets etc etc! This can manifest as any number of very odd problems, from low power shots, low recoil, to inconsistent cycling, the slide lock or bolt locks don't work, doesn't always load the next round and sometimes seeming to fire in full auto on semi (more on pistols that last one!).
So you want to look at ways to keep your gun firing well, regular cleaning is a must, lubrication, keep everything clean & oiled and they'll keep on trucking. Short Controlled Bursts! No point in airsoft is that phrase more relevant than with a GBB, you see a lot of videos showing 'full mag dumps' just to prove the GBB can do it, that's fine in a 25 degree+ shop, but out in the field it just doesn't work and is pretty impractical too, there's no point going toe to toe with someone holding their finger on the trigger of a 300 round hi-cap fed AEG when you've got 30 rounds, you have to make your shots count!
Performance varies greatly from gun to gun, a GHK M4 can mag dump at 12 degrees or lower, but a WE M4 may well have cooldown problems, but that's why the GHK costs half as much again as the WE (that and the GHKs tend to come with pre-reinforced internals too!). With all of these because of the forces involved everything wears, parts do wear out, if you don't keep up with your regular maintenance everything will wear out faster. The Spare parts (original and aftermarket upgrades) lists are huge, when something breaks you can choose from a straight replacement or all singing, all dancing reinforced parts.
Last problem you may run into with a lot of GBB (rifles especially, but some long barrel pistols too) is power! A lot of these will be over powered out of the box (360-380+ over 400 has been known!), WE Europe have come on in leaps and bounds in making UK law & site friendly GBBs. You can also reduce the power of some GBBs with a NPAS valve made by RATECH. Every GBB we sell is chronoed and either fitted with a NPAS or reducer to make it UK friendly below 350 FPS with 'Green Gas'.
Then we come to different pressure gases... This is a whole other article in itself! Basics are the lower the pressure, the safer it is for your GBB, but the weaker the powered shot & felt recoil. When it gets colder you can start looking towards higher powered gas, but the further you push it, the more chance you have of doing damage to your GBB. 90% of GBBR (rifles) will run perfectly on 'Green Gas' (as well as any metal slide pistol) without having to look at silly powered gases in summer, when the temperature drops that's when the fun experimentation starts!
That said, I love my GBB guns and I'm currently in the process of adding another one to my personal collection, they're just so damn fun!