Compressed Air in NBB`s

Popanddrop

Can you use compressed air in NBB`S?

Genghiz Cohen

Some guns are made to take air, some take CO2 some take HFC134a or Green Gas.

I don't know if the gases are interchangeable, but I'd doubt it.

NakedDex

Popanddrop wrote: »

Can you use compressed air in NBB`S?

No.

Popanddrop

thanks lads just thought I would find out due to my friend(masterofall) has a air compresser.

ED E

FYI the reason it doesn't work is that compressed air doesn't freeze. The other gasses are cold when compressed and mixing with warm air very rapidly expand. Air on the other hand is quite slow and wont give you enough power unless you used a much higher pressure. That kinda pressure might be dangerous, i dunno how high it'd have to be.

*Mental Image of exploding mags blowing off leg:eek:

NakedDex

It's not because air doesn't freeze, it's because air is a combination of gases who's combined mass requires a lot more pressure to liquify.

This is taken from ASI where I did some research into this topic a number of months ago when the same question came up. (LB You posted on this particular thread so you should know this).

GBB mags are actually liquid fill canisters. Although technically these are gas powered guns, they don't store gas in the mag, they store a liquified form of it. The various versions of gas are available for different power levels due to different liquid compression ratios. Once you pull the trigger, you release a small amount of gas and it's rate of expansion in it's new atmosphere (ie. a non pressurised one, unlike the sealed tank it was contained in within the mag or bottle) is what gives the propulsion to the BB. Different gasses produce higher or lower rates of expansion when released into standard atmospheric pressure. This is what gives the higher or lower muzzle velocities and overall power.

I haven't done any tests into the pressures of the gasses but it's more the expansion ratio I'd be looking to compare propane. Compressed air is just that, compressed. Not liquified like propane, butane and most other gases, hence why they need much larger tanks. This is due to the high content of Nitrogen in atmospheric air. Nitrogen does not compress to liquid form easily and when it does it becomes an endothermic liquid, liquid Nitrogen, aka that stuff that can freeze anything upon contact to almost 0 degrees Kelvin. Compression of Oxygen is more dangerous than difficult. Liquid Oxygen (lOx) is used as a component of rocket fuel as well as obvious medical apps. Therefore it's controlled (afaik)

Out of curiosity I tried using straight butane with a squirt of silicone and it does work though with not nearly as much power as propane seems to. Also, I could only just get through a mag before it emptied so it's compression qualities clearly aren't as good as propane either.

Turns out the temperatures for liquified air are seriously cold. Propane liquifies at 231K which is about -20C, Butane Liquifies at 273K which is about -.5C and CO2 sublimes at between 216K and 195K. CO2 doesn't have a liquid form, it's an odd gas like that. It goes directly from gaseous form to a solid (dry ice), hence why you always need a big thick tank to carry a lot of CO2.
Air liquifies at 100K which is -173C, a totally unmanageable temperature for practical use in airsofting.

Temperature is only a factor with regard to storage. Compressed air isn't used, not because it's not powerful enough, but because in liquid form it needs to drop to 100k as I explained above and in it's gaseous form it's not dense enough to store a useful amount in a mag. Same with CO2, that's why paintball markers have big tanks rather than a small powerlet

Genghiz Cohen

I have heard of a M16 that runs on compressed air. As you'd expect you need a big tank to operate a rifle all day, but it worked because the air didn't change temprature and made prolonge full auto possible.

NakedDex

They're constant feed units though. Usually on a backpack mounted tank. They use them for the M134a Vulcans too. Clumsy yokes to use and it means you can't leave it down because it's connected via airhose to your back.

NakedDex

Lethal_Bullet wrote: »

*Mental Image of exploding mags blowing off leg:eek:

Also, no mag will ever blow up on your leg no matter the pressure. In the unlikely event that you manage to pressurise it enough for it to be dangerous, the valve is designed to blow the seals and shear the threads to allow the gas somewhere to safely escape to. If they didn't they wouldn't be in production.

Genghiz Cohen

NakedDex wrote: »

They're constant feed units though. Usually on a backpack mounted tank. They use them for the M134a Vulcans too. Clumsy yokes to use and it means you can't leave it down because it's connected via airhose to your back.

Thats the one!

RC car fanatic

http://www.youtube.com/watch?v=vwOoTIRBiEo

Genghiz Cohen

RC car fanatic wrote: »

http://www.youtube.com/watch?v=vwOoTIRBiEo

The ROF on those things is insane.