Question about propellant for GBB

[Khyber]

Hey, so excuse my naivety of being new to the sport, but... I was pondering on the thought about HPA vs Propane or 'green gas'. Obviously HPA as a propellant is much cheaper than propane. But I don't like the idea of tapping via a line either. So could someone enlighten me as to why a gas mag needs the likes of propane etc. And as to why you couldn't theoretically fill a gas mag with HPA somehow? Is it to do with the pressure levels. Is HPA under a lot more pressure for the same volume of effective propellant thus meaning a gas mag wouldn't be strong enough to contain enough compressed air at the required pressure? May seem like a stupid thought and I'm sure if it was possible it would have been done already but I am genuinely curious as to why HPA needs to be tapped and not just contained within the mag?? 

[Guest]

1 hour ago, Khyber said:

Hey, so excuse my naivety of being new to the sport, but... I was pondering on the thought about HPA vs Propane or 'green gas'. Obviously HPA as a propellant is much cheaper than propane. But I don't like the idea of tapping via a line either. So could someone enlighten me as to why a gas mag needs the likes of propane etc. And as to why you couldn't theoretically fill a gas mag with HPA somehow? Is it to do with the pressure levels. Is HPA under a lot more pressure for the same volume of effective propellant thus meaning a gas mag wouldn't be strong enough to contain enough compressed air at the required pressure? May seem like a stupid thought and I'm sure if it was possible it would have been done already but I am genuinely curious as to why HPA needs to be tapped and not just contained within the mag?? 

Compressed air in a mag won’t work, masses more energy to compress it, so much stronger mag required.

Then, you need a regulator to bring the pressure down from stupid levels (3000psi) to propane equivalent (110-120 psi ish) 

 

Im sure it’s technically possible to do it, but you’re better off with a Devil Hunter mod to run CO2 in propane mags

[heroshark]

Yep basically that, you wouldn't get the capacity of shots using hpa in a mag size container. If you want a gbb gun that runs well it's all about the choice of gun and some model co2 Mags are just not worth bothering with imo over a gun that runs well on green gas. Even if you need to give it some more pep in winter using black gas.

Edited November 18, 2021 by heroshark

[Khyber]

Perfect answer. Just as I suspected, thanks for clearing that up. Curious as to what this devil hunter mod is though.... I'm off to learn some more. Thanks  

[Adolf Hamster]

the "gas" in a gbb magazine is a mix of liquid and gas.

 

when you fire the pressure drops, liquid portion starts boiling and the pressure raises back up, this is also why they tend to not like colder temperatures as the equilibrium pressure, and the rate of boiling will decrease. same reason why they don't like being fired quickly (where you're venting gas pressure faster than the boiling can top up)

 

it's not perfect, but it approximately keeps the pressure the same (close enough for our purposes) as long as there's liquid left in the magazine. if your familiar with cheap gas lighters it's exactly the same principle (and you can even see the liquid portion decrease over time in the transparent ones).

 

for hpa, this isn't the case, it's 100% gas, so to acheive a usable working volume it has to be compressed to much higher pressures then regulated down to the pressure you want to use. it's not really practical to build all this into a small enough package to fit inside a magazine hence using an external tank+regulator.

 

there are systems out there, notably the daytonagun kits, that operate like a gbb only with the air feed going through the gun rather than the magazine so you run it with a standard hpa setup. afaik the WE p90 can also be made to work like that due to the way they worked around the top mounted magazine.

[SBoardley]

1 hour ago, Khyber said:

Perfect answer. Just as I suspected, thanks for clearing that up. Curious as to what this devil hunter mod is though.... I'm off to learn some more. Thanks  

Dh mod is generally used in ghk platforms, where the outlet valve is replaced to hold the pressure of liquid CO2. The magazine can then be filled using something like a sodastream bottle. This is supposed to be

1. cost effective 

2. usable all year round

but can wear stock fcg, bolts, bolt stops fast. Has also been known to eventually blow you spring etc out the end of the buffer tube/ receiver extension!!

[Khyber]

Thanks for all the info chaps and answering without criticising what, to some may seem like a stupid question. Confirmed my assumptions. 

[Rogerborg]

It's a great question to ask, and much of airsoft development is the story of people who have been determined to try what's "not possible".

 

However, on this one we're limited by physics. Air is mostly nitrogen, and (wizardry ahoy), nitrogen doesn't compress well compared to something spicy like propane.   I believe that CO2 compresses even better, but I'm too scared to try it after seeing a mis-fitted CO2 bulb literally[*] rocket around a safe-zone.

 

[*] In the literal sense of both literally, and rocket.

[heroshark]

34 minutes ago, Rogerborg said:

It's a great question to ask, and much of airsoft development is the story of people who have been determined to try what's "not possible".

 

However, on this one we're limited by physics. Air is mostly nitrogen, and (wizardry ahoy), nitrogen doesn't compress well compared to something spicy like propane.   I believe that CO2 compresses even better, but I'm too scared to try it after seeing a mis-fitted propane bulb literally[*] rocket around a safe-zone.

 

[*] In the literal sense of both literally, and rocket.

I've co2 bulbs seen a fly before and dent a car 😂. Only an issue with QR ones, most are screw.

[Rogerborg]

27 minutes ago, heroshark said:

Only an issue with QR ones, most are screw.

 

I won't pretend to know how this one was weaponised. The bigly genius involved may have been sufficiently determined to unscrew one fast enough to turn it into an eyeball seeking missile.

 

That's another thing about airsoft: there are plenty of mistakes that you'll only make once, but there's never a shortage of folk ready to make them.