The reason that PCP has overtaken Co2 (Co2 was the choice of competitive shooters not so long ago) is that Air is more stable pressure wise at varying ambient air temperature. For example, a change from 10oC to 25oC would cause a few Fps difference in a PCP rifle and +-30fps diff in a Co2 rifle. Also Co2 has a peak power at +- 800fps in .177 (it can be increased but it requires running the rifle on Co2 liquid, but this can cause very dangerous pressures of over 200bar!!!!), it is governed by the speed of sound through the gas/ liquid.
But don?t be fooled Co2 can be very consistent when the rifle is tuned and the rifle is running with sufficient liquid gas to allow rapid replacement of gas used, the rifle can run at less than 3fps variance!!
Guido and Allan, you are both wrong to a point. Allan, the dive tank being tested, great!! What about the rifle? The rifle is holding the same pressure as the tank 95% of the time!
Guido, Co2's general working pressure is 900psi or +-62bar, but it is allso not stable as to temperature increases, A tank 100% full of liquid Co2 can reach 6000psi or just over 400bar!! Co2 cylinders are also supposed to be Hydro'ed one every 4 to 5 years, all PCP rifles should be visually inspected every 18 months to two years.
Both systems work on high pressure gas, trust me 50bar or 200bar can kill you just as dead! Both types of PC rifle system should be treated with respect and kept out of extream temps as well as no petroleum based lubricants should be used.
Boondock, the answers to your questions are also in the text above.
Off on the wrong tack there Allan. I assume you are asking re ?large changes? in the Co2 tank, yes I said that in the previous reply, both PCP and Co2 are potentially dangerous and Co2 is intolerant of Hi temps.
As for rust, most bulk Co2 tanks are aluminium and the steel containers (powerletts) etc, are cadmium plated.
I am not saying either one or the other is ?safer? as both involve pressure, 60bar is just as dangerous as 200bar, I am trying to get folks to understand that any pre-charged rifle should be dealt with, with care and the respect it deserves. I don?t want someone doing something stupid with Co2 because they think is ?safer? than compressed air!!
Also BIG POINT Co2 rifles are not designed to run on compressed air pressures.