hpa bb gun questions

[palanit]

I'm making a hpa powered bb gun (unless someone can convince me to use co2 instead). I want to regulate psi down to about 300 psi because most of my valves won't be able to handle anything more than that (300 psi is already pushing it). I am wondering how big I should make my chamber so I can get a lot of shots from a 48 ci air tank and still have a lot of power.
Edit:
My chamber is 3/4" type k copper pipe , I'm wondering how long I should make it

[jackssmirkingrevenge]

You don't need a lot of volume, but it depends on your reload mechanism efficiency too. Have you tried using GGDT? http://thehalls-in-bfe.com/GGDT/

[palanit]

I am using a minimatic air cylinder.
Edit:
If I made my chamber 24" with 3/4" pipe with air from an hpa tank regulated down to between 200-300 psi, how many shots could I get from a 3000 psi 48 ci hpa tank. I tried to do the math, but got a pretty low answer (like around 50) so I think I did the math wrong.

[jackssmirkingrevenge]

If I made my chamber 24" with 3/4" pipe with air from an hpa tank regulated down to between 200-300 psi, how many shots could I get from a 3000 psi 48 ci hpa tank. I tried to do the math, but got a pretty low answer (like around 50) so I think I did the math wrong.

First off, that's far too big for a 0.177" launcher.

Secondly, your math seems to be OK, I got 45 shots at 300 psi.

You can easily make it 6" long and get almost the same power, but 180 shots per tank.

[palanit]

About how much fps could I get from a 6" chamber. I am using a qev and 4 way valve as the pilot. Also how many shots could I get from a 20 oz co2 tank with a 6" chamber.

[jackssmirkingrevenge]

About how much fps could I get from a 6" chamber. I am using a qev and 4 way valve as the pilot.

Try and model it in GGDT, or take the easy way out (less guaranteed to work): http://www.spudfiles.com/forums/ggdt-hg ... 23256.html

Also how many shots could I get from a 20 oz co2 tank with a 6" chamber.

Science.

[Crna Legija]

yeah use GGDT and for god sakes read the usage page not just ask us.