Yeah it wasn't the most scientific testing for chonoing on my part.. I did it almost a year ago, and those are the numbers roughly what I could remember.. So it may not be entirely accurate, the .20 and .29 are the only ones I'm pretty sure are around the right ball park.
But you're right. strong winds make it difficult to shoot something that far away with any kind of accuracy with SGMs.. but at least, if it's gonna be affected by the wind say 6 ft left of your target, you can roughly compensate and hope the wind stays the same. :P the SGM's seem to go straightest even with wind for me, until that point where it looses it's hop up momentum. I think it has to do with a combination of the hop up and wind, but my .36's go crazy about half the time, it looks like wind pulling it, but more likely a bad spin on the hop up in combination with the wind. The SGM's flight path looks really stable it's got that 'almost falling' equilibrium quality to it... the first 130 ft or so it really doesn't seem to be affected by any kind of wind or external factors. The .36's look like they're struggling to keep height. and .25's look like the hop up spin is about to tear the thing into pieces.
Maybe you're right though. .29's are the sweet spot for 450fps guns. maybe .30's are the ones for 500fps.
Oh! forgot about one last note, sort of related... Heavier bb's tend to hurt more (duh right?). When I was using .36's people complained once in a while even when the range was pretty far. I've shot my buddies at gbb range with .29's with only minor reports of pain. I wouldn't do the same thing with a .36... Although sometimes people don't feel the SGM's hit at long ranges.
As for the FPS drops for weight. Are you using a spring or a gas rifle? I heard gas rifles tend to loose less FPS for weight.. barrel length might also be a factor.. (mine's 495mm) But my fps drops are quite significant.
I have 2 personalities, Telkin and Valcrow.