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BB gun/ Pellet gun plans

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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BB gun/ Pellet gun plans

Unread postAuthor: CannonCreator » Thu Oct 04, 2007 12:14 am

K so I am designing a pneumatic bb gun/ pellet gun (not airsoft). I am going to pull a barrel out of a real BB gun so I can get a perfect fit for the bbs and pellets. Its also going to be all steel, and triggerend by a piston valve.All I know about the piping so far is that everything is going to be under 3/4" EXCEPT for the chamber and reducer. My question is this. I want it to reach 1000+ fps, and have it be fairly accurate, so how big and long should I make the chamber?

Would a 9oz co2 tank be to big?

Would it even be possible for meto reach 1000FPS + ?
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Unread postAuthor: Marco321 » Thu Oct 04, 2007 12:19 am

Use GGDT, but for BB guns, you need a small chamber at a high pressure, around 300psi. Take a look at this Thread on it, it is basically about what you are asking.
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Unread postAuthor: CannonCreator » Thu Oct 04, 2007 12:29 am

ok so I guess acording to jacks calcualtions I would want a 1 inch chamber filled to 1600psi ?!?!


So I should go small length chamber and a high PSI

can I get 1600PSI in a 2" long 3/4" diameter chamber with a shcok pump?
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Unread postAuthor: hi » Thu Oct 04, 2007 12:51 am

CannonCreator wrote:

can I get 1600PSI in a 2" long 3/4" diameter chamber with a shcok pump?


probably not, but if you put your mind to it you can do anything...
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Unread postAuthor: Marco321 » Thu Oct 04, 2007 12:52 am

1600 is twice the pressure of unregulated CO2, i don't know many people who are game to use unregulated CO2, let alone twice the pressure of it.

I would go with around 300-400psi if you have the skills (I'm not ragging on your skills, but 300psi is no toy) and a precisely made piston valve with minimum pilot volume and a light well made piston.

EDIT: If you REALLY felt the need, you could rig up a pneumatic ramrod to pump the gun up using the shock pump :P
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Unread postAuthor: jackssmirkingrevenge » Thu Oct 04, 2007 1:30 am

If you want to get 1000 fps+ I would suggest going for air from a shock pump or a regulated HPA bottle rather than CO2.

There are plenty of threads on small high pressure BB projects if you search. Have a look here, with a 5 inch long 3/4 inch I/D chamber at 300-400 psi I got well over 1,000 fps with a 0.25 gram BB - though this was with a burst disk valve.

I am going to pull a barrel out of a real BB gun so I can get a perfect fit for the bbs and pellets


Chances are that's going to be far too short to give you decent velocity, when it comes to obtening high speed those extra inches matter ;)
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Unread postAuthor: Novacastrian » Thu Oct 04, 2007 2:14 am

If you want more inches, STROKE IT, otherwise go for a longer barrel :P
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Unread postAuthor: Redcoat » Thu Oct 04, 2007 3:04 am

If you eant a single shot pellet gun, do what MArco suggested, you need a small chamber perhaps 2cm by 4cm. and pump it up goodly.
Use a shock pump. But the good thing is if you can mount the pump on your gun then it will be like a multi-stroke air rifle/pellet gun.
Like the classic Daisy HOw I want one. Maybe when i finish my piston valve I'll try and replicate one. :idea: .
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Unread postAuthor: jackssmirkingrevenge » Thu Oct 04, 2007 3:22 am

Redcoat wrote:Like the classic Daisy HOw I want one.


Walther make a CO2 powered Winchester style lever action that gives you more than twice the velocity ;) I believe there also was a Winchester replica chambered for Brocock air cartridges.
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