I also follow the same line of thought as Geo: the more joules I fire with the better.
THIS is also why I run a shorter barrel, at only 400mm, as shorter barrels allow for "energy creep"
Energy creep is a term that describes why I have a higher muzzle power (joules) with higher weight BBs than lower weight BBs.
What does this mean? Well, when I chrono with .2gram BBs, I'm field legal at 498fps which is 2.26 joules of energy.
BUT when I chrono with .4gram BBs, my muzzle energy is a massive 2.66 joules. That's an extra .4 joules of energy from the same rifle. This rifle is still field legal according to field rules, but has a much higher energy rating now. If I convert 2.66 joules back to .2gram, that's roughly 550fps!
So why is this? I'm not 100% sure, but I believe because the .2gram BBs accelerate so quickly, they leave the barrel before all of the air from the cylinder "gets behind it". Because the heavier BB is more massive, it takes longer to accelerate from 0 and therefore has longer time for greater air pressure build up behind it.
This is just one "trick" that allows me to out-range other players on the field- energy creep gives me that extra little bit of oomph.
EDIT: so whilst I'm here Geo:
6 foot 3, 498fps,
2.26 joules on .2s
2.66 joules on .4s.