First up a map of airsoft sites courtesy of Airbana

All airsofters at some point spend time trawling the net for information on springs, fps conversions or other useful references. So to try and help you out we’re going to gather a few handy references here for you to download. Just click the images to view full size and then right click and “save as” to download.
Springs
Not an exact science but a rough guide to the fps produced by most of the major spring manufacturers

Simple FPS Comparison
This small handy “ready reckoner” compares the standard fps limits from a standard 0.2g BB to other weights, so you can find out what your 0.29 grand master should be doing!

FPS vs BB weight comparison

Muzzle Energy
A more detailed table of muzzle energy calculations, so you can see why everyone gets so excited that your sniper rifle is “only” 20 fps over the limit! All the figures in joules.

Muzzle Energy

For those with a GP68 wishing to use it with PMR radios. First ensure you are operating within the law for transmit power, but for setting up and frequencies click the link here…
Guide to the GP68 Programing