SpudFiles

for my next gun I am thinking of using a propane injection system and I was wondering how much psi a small camping propane tank has in it ?

Depends on the pressure. I think at about 65*F it's around 90PSI. If it's hotter, the pressure can easily go into the hundreds.

It's best to use a regulator when building your metering system, and use a meter that requires anywhere from 45-70 psi to get the proper load. That way it will still work in colder weather.

One like this works fairly well.

well, you can go through a long series of calculations to figure out the vapor pressure of propane at whatever temperature you have, or look at a website that does it for you: http://www.s-ohe.com/Propane_cal.html

Basically, the pressure will be around 80-140 PSI, unless you shove the thing into an oven, which is a bad idea anyway.