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CO2 or air for rifle

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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CO2 or air for rifle

Unread postAuthor: joepage2008x2 » Fri Mar 05, 2010 6:09 pm

Hi, im making a bolt-action or semi-auto air rifle, it will be a stealth rifle that I can take apart and fit into a small case. I will be running it at an operating pressure of around 200-300psi. Most PCP air rifles are air but at 3000psi (dont like these pressures), Its not common to see CO2 powered.

Here is my question, why is co2 uncommon for high power air rifles and is air any benefit to co2?

Another question, what pressure can the average 15 and 22mm copper tube hold?

I will post some pictures of my prototypes in future - probably be bb gun instead of pellets first. I have also invented new type of electric valve - not the same as the daystate rifle valves. Only has 5 moving parts in all rifle- trigger lever, single part in valve, boltaction or semi-auto assembly, pressure reg, pellet. Should be reliable and easy to service.
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Unread postAuthor: Demon » Fri Mar 05, 2010 7:20 pm

Cooper pipe can hold 800 psi, depends on the sizes, search for more information.

300 psi would require a petrol drum sized airtank to work on a pcp airgun
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Unread postAuthor: Patto » Fri Mar 05, 2010 8:13 pm

you do find c02 air rifles look at the gamo air rifle, 200 shot's off a 88g c02 at 800 fps with some pellets . Hpa will give you better consist. With more power altho the power you get from c02 (850 psi) is nothing to joke about either . With brass / copper make sure you check the rating and search the forum , there are some really good post here about pressure ratings.
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Unread postAuthor: Crna Legija » Fri Mar 05, 2010 8:39 pm

co2 it more dense than air so it moves slower thus not at powerful.
co2 is around 800-1000 psi and very temperature dependent. hot days you have more power than cold days.
also if you have a pcp pump you get free 3000psi, co2 you have to pay for

this will help you with you copper pipe

if you unsure fill you gun will water all the way up then pressurize it
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Unread postAuthor: Hubb » Fri Mar 05, 2010 9:17 pm

CO2 is an excellent 'fuel' for high powered homemade launchers. Those high powered air rifles you are referring to, are they spring piston types? If so, they operate differently than a pneumatic air rifle, which would explain why CO2 is not too common.
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Unread postAuthor: qwerty » Sat Mar 06, 2010 8:01 am

what pressure can the average 15 and 22mm copper tube hold?


I've had 15mm up to 320psi and i reckon that 500 would be fine.
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Unread postAuthor: jackssmirkingrevenge » Sat Mar 06, 2010 8:19 am

As expressed above, CO<sub>2</sub> is denser than air so for the same pressure it will give you a lower velocity than compressed air. It is also much more sensitive to temperature changes than air, so tends to be much less consistent.

As an example, look at the performance of the CO<sub>2</sub> and air powered versions of the Condor pneumatic.

Operating at lower pressures will probably give disappointing results in small calibres like 0.177" and 0.22", you might want to consider moving up in calibre like the Quackenbush Outlaw.
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Unread postAuthor: joepage2008x2 » Sat Mar 06, 2010 2:29 pm

The gun will be firing .22 pellets - i know that its very hard to get high velocities and a lot of air is used when using .177.

I know CO2 does vary a lot with temperature, I will be using a pressure regulator not straight from the source because I want it to have consistant power levels.
The rifle will have two tanks, the high pressure source and the operating pressure tank. The copper pipe will do for the lower pressure tank.
Im just wondering how much my regulator will go out when under operation because it will cool and may allow more or less pressure to flow.

Gamo are the only common rifles that use co2 that I have come across, I do not have a rifle pump and can only get 400psi from my compressor. There is a scuba diving shop a few miles away so i may be able to get air from them - I dont want to pay a lot of money though.

I really like that condor pneumatic - has far more power than the co2. I live in the uk so can only go up to 12ft/lb, not saying I wont I wont go over :wink: The great thing with my design is that I can adjust power electronically. I think I will try co2 first as power levels arnt too high.

My next question is, I will be operating at 300psi, I will be using a silencer, even though these pressures are the same will one need a larger area in the silencer than the other. (larger silencer)
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Unread postAuthor: Patto » Sat Mar 06, 2010 7:26 pm

My next question is, I will be operating at 300psi, I will be using a silencer, even though these pressures are the same will one need a larger area in the silencer than the other. (larger silencer)



huh - ???? Are you talking between c02 and hpa Or pressures?
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Unread postAuthor: D_Hall » Sat Mar 06, 2010 7:42 pm

joepage2008x2 wrote:My next question is, I will be operating at 300psi, I will be using a silencer, even though these pressures are the same will one need a larger area in the silencer than the other. (larger silencer)

A properly sized barrel doesn't require a silencer if all you're pushing is 300 psi. They can be almost arbitrarily quiet.
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Unread postAuthor: joepage2008x2 » Sun Mar 07, 2010 3:02 pm

Im talking about air and co2 at 300psi, i was wondering if one would be louder than the other because of the different densities.

My barrel will be between 300-400mm, my last gun that used bb's at 200psi and had a barrel 300mm long - it was noisy. A silencer is a must - suppose I can experiment with different pressures and different sized silencers.

Im half way through my valve - I will post pictures when I have a working prototype. I built a valve before but was from scrap and really inefficient - this one should be great.
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Unread postAuthor: jackssmirkingrevenge » Sun Mar 07, 2010 3:30 pm

With a good valve and a relatively short barrel it will be loud, in my experience even a low powered commercially available CO<sub>2</sub> pistol tends to be disproportionally noisy compared to much more powerful pneumatics and springers.

I can experiment with different pressures and different sized silencers


The rule of thumb here is that there is no substitute for cubic capacity, make it as big as you're comfortable with. Diameter is more relevant that length, a 40mm diameter silencer 100mm long has double the capacity of a 20mm silencer 200mm long.

I really like that condor pneumatic - has far more power than the co2.


It's sold in the UK as the Gunpower Stealth, itsinline hammer valve makes it one of the most efficient pneumatics on the market.

I live in the UK so can only go up to 12ft/lb, not saying I won't go over


Note that UK law explicitly states that an airgun capable of exceeding 12ft/lbs of muzzle energy is an illegal weapon without a FAC - saying that you only use it at lower levels is no defence - so it is still advisable to keep a low profile.
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Unread postAuthor: joepage2008x2 » Sun Mar 07, 2010 5:43 pm

I can only test it on air first anyway, I think I will give co2 a miss. I have a springer and its supposed to be one the the quietest rifles - a tx200 airarms (im not too sure). I would like to compare them.

I wonder how efficient my valve might be, It is a new design and never been used (must be some reason).

My rifle will not be capable of powers over 12ft/lb, Im only going to use it for short range hunting. I will get an FAC otherwise. I may just stick to airsoft and be on the safe side, it all depends if this valve works.

The gunpower stealth is just what I want and the price looks ok - maybe a future rifle for me.
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Unread postAuthor: jackssmirkingrevenge » Sun Mar 07, 2010 5:48 pm

I wonder how efficient my valve might be, It is a new design and never been used (must be some reason).


Care to share the design?

My rifle will not be capable of powers over 12ft/lb, Im only going to use it for short range hunting.


Alas, the rules:

Discussion of shooting anything at any person and/or animal is prohibited, and may result in a permanent banning of your account.
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Unread postAuthor: joepage2008x2 » Sun Mar 07, 2010 6:03 pm

I will share the design if I get it working, shouldnt be too much longer. I posted one on here before but was made from scrap and really inefficient. I managed 5 200psi shots at over 600fps with 300mm barrel from just a 100cc tank at 200psi, 10 shots over 300fps. Im not sure how good this compared to others.

Sorry, it was a long time since I went on this forum and I forgot this rule, I will say target shooting next time.
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