Hey there,

I've recently bought a Crosman 1077 airgun and I was
just wondering if I could replace the CO2 tanks
with ordinary O2 tanks (as used in breathing equipment).

Also, I would like to know what the pressure on
a 12 gram CO2 cilinder is.

Thanks in advance

of 900 psi depending on temperature.  It has that pressure weather you have a thimble full or a tank truck full. CO2 is not pumped up in  pressure like air is.

Thanks for that reply,

that would really help me out.

It's cheaper for me to refill air cilinders (which I can do for
free) instead of buying 12 gram CO2 cilinders all the time.

So I started wondering if there was a different gas that
you can use instead of CO2.
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By the way,

If you use Liquid CO2 your 1077 will shoot faster and therefor more
accurate. The bottom of the standard, crosman CO2 cilinder contains liquid
CO2 but this runs out first and that's why you will loose power
after a few shots. So if you use a cilinder that only contains liquid
CO2 you will be able to take some more shots and have a higher rate of power.
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I think I just found the answer to my own question...

Carbon Dioxide (C02)

-Stored as a liquid in cylinders and expands into a gas,
-Cannot fill compressed air or nitro into CO2 tanks,
-Cylinders typically can screw right into an ASA and has a pin valve,
-Output pressure depends on environment temperature.... 80*f is about 950psi.... 40*F is about 550psi,
-Capacity of tanks is measured in ounces,
-This gas causes velocity jumps due to liquid expansion,
-Most are made of either steel or aluminum,
-Aluminum cylinders over 2" in width needs to be tested every 5 years by hydrostatic testing,
-You can get CO2 in disposable 12g cartridges to a refillable 20oz tank,
-You can get refills pretty much at any field or store,
-When shooting with CO2, the tank will get cold. The colder the tank, less air pressure.