Big power difference on air vs. CO2

[Dave S]

FWIW, I took an original .177 Mac-1 QB 77 from the mid '90's and did a temperature test this morning. Bulk-Feed Co2 chamber was at 75 degrees F. using an IR thermometer. Ambient temp in my attic was 82 F. Did a 4 shot string. Then I super-heated the Co2 chamber by placing the entire gun in direct sunlight for 5 minutes raising the gun temp to 107 degrees F. The sheet below should demonstrate the radical difference in velocity concerning Co2 temperatures. Which proves to me that with Co2, every time you field shoot, the gun must be field calibrated. HPA vs. Co2........Apples and Oranges! dave

[Ribbonstone]

Just looking at it a different way.

IF I had a non regulated PCP that kept shooting faster and faster the higher I filled it....would think that it might be smacking that vlave  a little hard.

[Dave S]

Just looking at it a different way.

IF I had a non regulated PCP that kept shooting faster and faster the higher I filled it....would think that it might be smacking that vlave  a little hard.

That's called "The Law of Vanishing Returns!"  dave

[Hoosier Daddy]

Interesting... or better put shocking.
I have an Xisico XS60-C with a bulk fill end cap, and a Sheridan Model "F" with a bulk fill insert from Timmy Mac.
 I have a paint ball bottle with a standard 850psi Reg I can teather them to with HPA.
Ambient temp here has been around 80-85 degrees when I get home from work or mid morning shooting on the weekends.
I have never compared the two propellants, just used air when it was colder than C02 likes...
 I will dig out my chrono and run them both across and see what happens side by side.

[Ribbonstone]

That Sheridan F will be interresting.....had one long ago,was a gas hog but a pretty powerful co2 rifle....suspect you might find a lot of difference there (never did try that while I had it).

(But..be careful...that's an air tube never made to hold pressure...co2 or Air....and it kind of not worth it when the barrel seperates from the gas tube.)