What Gas to use in a KWA M9?

[cammi]

Hello I have recently bought my first GBB Pistol and it's a KWA M9. I read online that Abbey Brut Sniper Gas is a good gas to use on this gun so I bought a canister of it. I don't know if this is me doing something wrong or if it's the gas but sometimes when I pull the trigger A surge of Gas starts coming out from all parts of the gun and sometimes on the last shot the slide doesn't slide back that far. The manual says to fill the gas mag until it overflows but I am not quite sure when I know it is overflowing? Also am I using the right gas for this gun?
Thanks in advance!

[PureSilver]

Re: What Gas to use in a KWA M9?

I don't own a KWA M9, but I might be able to help with a few of your queries.

I read online that Abbey Brut Sniper Gas is a good gas to use on this gun so I bought a canister of it. I don't know if this is me doing something wrong or if it's the gas but sometimes when I pull the trigger A surge of Gas starts coming out from all parts of the gun and sometimes on the last shot the slide doesn't slide back that far.

I'm guessing that this phenomenon occurs when you have been shooting the gun rapidly? What you are experiencing is called a 'vent'. Every time you fire the gun, the magazine releases a small amount of gas to power the shot. This causes adiabatic cooling - the magazine becomes very cold because of the release of pressure. When you fire the gun too quickly, the freezing gas escaping from the magazine cools the magazine's valves to the extent that they freeze open, allowing all the gas to surge out in one go. You should be able to avoid this by restricting your rate of fire or switching magazines preemptively if you can feel the gun becoming sluggish.

When the gun is fired repeatedly, as before, it becomes very cold. That means that the gas vented for each shot is so cold that it doesn't expand as quickly, which means that more of it escapes the magazine before the expanding pressure can cycle the slide. This means that the gun can run out of gas before it has fired all its BBs - and even if it does fire all the BBs, it might not have sufficient gas pressure left to lock the slide back afterwards. Again, you should be able to avoid this by slowing your rate of fire or preemptively switching to a new magazine that's still full of gas.

The manual says to fill the gas mag until it overflows but I am not quite sure when I know it is overflowing? Also am I using the right gas for this gun?

Liquid-gas magazines store the gun's operating fluid at pressure. Above a certain pressure the fluid is a liquid; below it, it is a gas. The liquid is heavier than the gas, and thus the liquid sits at the bottom of the magazine and the gas sits at the top. When you fill your magazine (holding it vertically upright with the gas bottle held inverted over it) liquid flows from the bottle into the magazine. This displaces some of the gas that previously filled the magazine, causing it to sputter and hiss from the fill valve. When the magazine begins to spit liquid (you'll know because little blobs of freezing cold will land on your hands), it is overflowing, and therefore full.

I don't know quite what's in the gas you've bought, but chemistry is chemistry and try as they might airsoft manufacturers can't just create their own chemicals. Almost all 'high pressure' airsoft gas (which I'm guessing your 'sniper gas' is) is just unscented propane mixed with liquid silicone lubricant to maintain the seals in your gun. Your KWA is a relatively rugged pistol and should cope with any airsoft gas you can find in a tin. It should also survive various non-airsoft gas blends (propene, for example) but it will be quiet happy with ordinary Coleman propane, which is a lot cheaper than airsoft-labelled propane.