There have been experiments conducted showing that the bb wights does not affect distance traveled. Therefore, for the most accuracy and power against wind I would recommend something around .4g. Also I would make sure you have a good hopup as that greatly affects your range as well.
I'm using .43s now. My tanaka chronoed at 570 with .3s, and the hop had to be almost all the way off. Range seems to be improved with the new bbs though. Haven't had time to properly adjust the hop though.