I threw together a simple spreadsheet in Microsoft Excel to help me keep track of the numbers while working on my Weapon Expansion Mod (Shameless plug here). As things progressed I started adding in small calculations to keep track of what the numbers would equate to, calculating damage per second, accounting for accuracy and so on.
(http://i86.photobucket.com/albums/k91/ReaperDTC/Example_zpsqtqv9qci.png)
Because of how Rimworld works internally and certain things not factoring into the equations (Pawn accuracy, bullet speed, forced bullet spread and so on...) it isn't a perfect representation, but it should help give a rough idea of how powerful your weapons are.
It dawned on me that the thing might benefit someone else out there, so I threw it on dropbox and now I'm linking it here:
http://adf.ly/1gwT6X
Make sure you download it rather than just viewing it online as I doubt this will work. I don't know - I guess it might:
(http://i86.photobucket.com/albums/k91/ReaperDTC/Download_zpsyxvlgncm.png)