Indoor CQB can go as low as 330 FPS sometimes (basically 1 Joule). Outdoor, the generally agreed upon limit is 400 but may be higher or lower depending on host and field. Ie. a smaller outdoor field might be 360 or 380 while a larger outdoor field might have a limit of 420 or 425 (with specified Minimum Engagement Distances).
Aim for a speed of 360-380 on .20's. So an "M110" or "M120" is around the power rating of the spring you'll want to use. I was told once that the "M" rating is basically the speed you'll be shooting at in meters per second but I can't confirm this (however it does make sense if you do the m/s to fps calculations yourself).
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE