This is an Excel spread sheet which allows you to carefully examine the consistency of your gun. By inputting very minimal data, the spread sheet will automatically fill in the graphic charts, Standard Deviations, FPS Spreads for each 10 shot string and cumulative strings up to 100 shots, Average Foot Pounds, Accumulated Foot Pounds from the charge, And display results graphically. All important inputs have help Notes attached. Although designed primarily for PCP guns, this spread sheet will work for all air arms. You will need at least Excel 97 to use this Download (or openoffice free software). The Original designers of this Spread Sheet are Credited within the File. This is very simple to use and you don't need to be fluent in Excel. If you have never used Excel you will still be able to use this chart.
If you don't have Microsoft Excel and don't want to pay for it then download
Openoffice at http://download.openoffice.org/index.html
It's free and compatible with Microsoft files.
Here is a partial screen shot of the excel sheet.