Calling all those who have gas bb guns...

[cammyd32]

I am modding/building a bb gun. I have got the new mech worked (a cross between one of jsrs blow forward bolts and a paintball gun) out but I was considering the air supply. I have had loads of experience with compressed air tanks and don't like them because of their need to be large.

So then there I was thinking about low area eating compressed gas storage ideas and I had a thought, instead of using a gas which would have to be stored at stupidly high temperatures to store lots of it how about I have a gas that will be liquid at lower (about 120 psi) pressures so more of it can be stored in a reasonably small area without the need to pressurize it to stupidly high temperatures like propane or green gas like you get on a gbb gun.

What I would like to know is some simple details about gas consumption for decently powered bb guns, that and if there are any problems relating to gbb guns that i should know before investing in loads of steel parts for the mech and inbuilt tank.

Thanks

[warhead052]

Just buy a 20oz or bigger co2 bottle with a regulator. May not be what you need, but you can store alot of pressure in it with a small bottle.

[jackssmirkingrevenge]

Consumption depends completely on what sort of power you want to achieve and how efficient your design is.

For example, if you want 500 fps, you're going to waste a lot more gas than if you'd be happy with 350 fps.

A rifle sized package is going to need less gas per shot to achieve the same power as a pistol sized package because of the longer barrel.

A fast efficient valve will need less gas to achieve a given projectile velocity than a slow, low flow valve.

[cammyd32]

Just buy a 20oz or bigger co2 bottle with a regulator. May not be what you need, but you can store alot of pressure in it with a small bottle.

you have a point but then you are entirely reliant on some kind of hp compressor which costs thousands and I just don't have that kind of money!.

As for consumption the average amount of air used for each shot will be at about 70-110 psi to fill a 20 inch 6mm barrel. the flow will not be choked and it will be a straight line valve so no corners or areas to fill making it more efficient.
The valve itself will be really quite efficient as I am hoping the design will make it I am currently designing this on G-sketchup so pictures of the valve coming soon.
I am intending to shoot it at about 250- 400 fps so its safe for airsoft, I will add a hopup to increase range.

I hope that gives some more specific specs to base just a guess on types of guns with those specs and their gas usage.

[warhead052]

Not really, all you do is go back to were you bought it and buy another or have them refill it. Or, you get a fridge compressor, an old empty 20oz co2 bottle, and then compress 500+ psi into the bottle.

[cammyd32]

Yeah but that is still impractical, and imagine the cost of refilling that many times!!
To do that would still cost a fortune. and you would need a detachable tank.

[warhead052]

Not really, its not that bad. Just jb weld a T into the top, and put a pressure gauge and a fill valve in one side, and the connection to the other. not that hard.

[cammyd32]

I can see your point, but in my progect I am intending to conceal all the mech gas tank ect inside the gun body, can you see my perspective on hp air tanks now?

[warhead052]

Link me to the body? I can figure out an air source, but it may not hold high pressures.

[cammyd32]

When you say body I take it you mean what gun I am intending to fit it in.
I am trying to fit it into some kind of portable ww2 smg, like the model 55 reising or thompson, as I have always liked these types of guns.

[warhead052]

Thats what I mean. So a thompson? Just incorporate a co2 magazine kinda like gas blow back rifles.

[cammyd32]

Yeah but that then creates a load of problems including the need for a quickly open-able chamber for the cartridge with inside it a piercing spike, it then needs some kind of check valve which is opened when you attach the chamber, I did try this theory but it ended up routing loads of tubes through the gun making any sort of bodywork really flimsy and parts would have to bulge to contain it.
these train of thoughts are exactly what I had to come through to reach the conclusion I did about using a small liquid gas chamber inside the gun.
agreeably there is some credibility in co2 canisters but they just have too many complicated compulsory parts

[Lockednloaded]

How about propane? It's stored at a liquid and can reach about 120psi

[cammyd32]

How about propane? It's stored at a liquid and can reach about 120psi

exactly my point.
All I need now are some performance stats for it so I know how big I should have my reservoir.

[warhead052]

GGDT? Try that.