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12g CO2 Pump Question

Unread postPosted: Mon May 21, 2007 12:14 am
Author: shud_b_rite
If I have a CO2 bike pump with a 12gram non threaded cartridge that is completely empty (the same pressure as our atmosphere). What would happen if I attached it to the shrader valve of a bike that had its tires pumped to 100psi? If I pulled the trigger would air flow back inside the canister causing it to become pressurized, or is there a one way valve inside these pump things?

The reason I want to know is because I plan on building a air soft gun that uses a co2 pump to let air from the supply chamber into the co2 cartridge via a tire valve.

Unread postPosted: Mon May 21, 2007 12:45 am
Author: A-98
i dunno, try it out. theres no reason there should be a 1 way valve on the things.

but isnt the 12g co2 a tad small?

Unread postPosted: Mon May 21, 2007 1:00 am
Author: shud_b_rite
Call me cheap if you will but I don't want to buy one until I know. But I probably will go and get one now, if it doesn't do what I want it to do, then I'll make it. No I don't think 12g is too small for an air soft gun. From looking at the performance of my prototype I made which had a 750ml bottle at 40psi, I reckon it should work just as good with pressures up to 100psi. It will have a piston valve on it.

Unread postPosted: Mon May 21, 2007 12:20 pm
Author: goathunter
I'm planning on building an airsoft "pepperbox" by hooking up a 12 gram changer to a pressure washer handle.You might try that,would be cheap.

Unread postPosted: Mon May 21, 2007 1:08 pm
Author: ShowNoMercy
Is this going to be a single shot design? And why not just make a cloud or vortex design?

Unread postPosted: Mon May 21, 2007 1:19 pm
Author: leeeeshad
100psi in one of those is hardly any air atall, when there new they have liquid co2 in them, unless you have a few thousand psi pump i would get a bigger one

Unread postPosted: Mon May 21, 2007 11:20 pm
Author: shud_b_rite
It is only for one shot. The idea is that I can load a bb in the barrel. Pull the loading valve to charge up the 12gram tank from the main tank. Pull a trigger that will open the spring piston valve. I thought of using a pressure washer thing but it would then be hard to attach it to the co2 canister because of the threads.

I wish I knew where to get a tire inflater with gauge that wont leak when more than 100psi is put on the shrader valve end.

Anyway never mind, thanks people for your help.

Unread postPosted: Tue May 22, 2007 4:05 am
Author: Infernal Maveric
If you plan on making the BB gun do some decent damage, 100 PSi in the 12g canister will shoot the BB about 10 feet.

I just finished a QEV BB gun. Using about 9in of 28mm copper for the chamber, and only at 140+ PSi will it penetrate through steel sheet metal.

I'd either advise you to make the chamber bigger, or buy a new 12g cartridge for every few BBs you fire.

Unread postPosted: Tue May 22, 2007 4:27 am
Author: chaos
Infernal Maveric wrote:If you plan on making the BB gun do some decent damage, 100 PSi in the 12g canister will shoot the BB about 10 feet.

I just finished a QEV BB gun. Using about 9in of 28mm copper for the chamber, and only at 140+ PSi will it penetrate through steel sheet metal.

I'd either advise you to make the chamber bigger, or buy a new 12g cartridge for every few BBs you fire.


have you any evidence for that one?

Unread postPosted: Tue May 22, 2007 4:35 am
Author: shud_b_rite
Incase your wondering I am not planning on using a co2 pump to shoot a bb. I was thinking about taking an empty 12gram cartridge and filling it to 100psi (with air) by using a co2 pump in reverse. ie, instead of using the cartridge to fill a chamber, I am using a chamber to fill the empty cartridge.

No I am confident in my design. My crappy drink bottle prototype that I posted the other week will shoot at 275 fps at just 40psi, and the barrel isn't even sealed to the valve (I just hold it in front of it about 5mm away). If made properly I reckon I can get better performance from a smaller chamber.

Unread postPosted: Tue May 22, 2007 11:36 am
Author: clide
My CO2 tire inflater does not allow you to fill in reverse. Since the schrader is basically a check valve it will not allow flow back in. If you remove the core of the schrader then it will allow flow through, but the CO2 inflater vents upstream pressure when the trigger is not being pulled, so you will have a constant leak there. And it seemed to let air through in reverse when I was blowing on it, but when I hooked it up to the compressor it didn't let air through in reverse.

Unread postPosted: Tue May 22, 2007 12:07 pm
Author: Infernal Maveric
chaos wrote:
Infernal Maveric wrote:If you plan on making the BB gun do some decent damage, 100 PSi in the 12g canister will shoot the BB about 10 feet.

I just finished a QEV BB gun. Using about 9in of 28mm copper for the chamber, and only at 140+ PSi will it penetrate through steel sheet metal.

I'd either advise you to make the chamber bigger, or buy a new 12g cartridge for every few BBs you fire.


have you any evidence for that one?


Well, my bike pump is a steaming pile of excrement, that only goes u to 140psi. At 135psi, the BB will make a dent about a good 4mm into the steel, but at 140psi, the Bb will punch a perfectly clean hole through it.

(Pics are yet to be posted)

And as Clide said, the scharder is a oneway, it could be possible, but not easy.

Unread postPosted: Tue May 22, 2007 7:14 pm
Author: chaos
Infernal Maveric wrote:
chaos wrote:
Infernal Maveric wrote:If you plan on making the BB gun do some decent damage, 100 PSi in the 12g canister will shoot the BB about 10 feet.

I just finished a QEV BB gun. Using about 9in of 28mm copper for the chamber, and only at 140+ PSi will it penetrate through steel sheet metal.

I'd either advise you to make the chamber bigger, or buy a new 12g cartridge for every few BBs you fire.


have you any evidence for that one?


Well, my bike pump is a steaming pile of excrement, that only goes u to 140psi. At 135psi, the BB will make a dent about a good 4mm into the steel, but at 140psi, the Bb will punch a perfectly clean hole through it.

(Pics are yet to be posted)

And as Clide said, the scharder is a oneway, it could be possible, but not easy.


yer ok, i forgot to ask how thick was the sheet metal?

Unread postPosted: Tue May 22, 2007 7:20 pm
Author: VH_man
I think your idea for using a 12g cylinder for a pressure chamber is perfect. its small, compact, and can take high pressures. i think they thread into 1/8 inch brass fittings..... i might be wrong....... if not just epoxy it in.