Masterjuggler98 - In that thread that cheeseman said that 400fps is 'optimum' for a heavier (quoted 0.43) bb.
Everything I have ever read online (but particularly this: http://mackila.com/airsoft/ATP/) suggests that heavier bb's are better (so long as the hop is good enough to get the correct trajectory!) since they are subject to less air resistance (as they are slower) so keep their energy for longer and that they are less blown off course by the wind. However others have said that the 0.4g bb's are more variable and so they prefer to use lighter (but higher quality) bb's say 0.3 marushin super grand master or bbbastards etc.
So: 400fps still seems a decent choice for upgrading. But as always the main thing is not just the FPS but a whole host of other factors.
Also there's no explanation in that thread just an assertion ('do the proper modifications' is not an explanation unless the mods are explained, I would be interested in a proper explanation though). However it would appear that he believes 400fps is close to optimum for 0.4 bb's.
Everything I have ever read online (but particularly this: http://mackila.com/airsoft/ATP/) suggests that heavier bb's are better (so long as the hop is good enough to get the correct trajectory!) since they are subject to less air resistance (as they are slower) so keep their energy for longer and that they are less blown off course by the wind. However others have said that the 0.4g bb's are more variable and so they prefer to use lighter (but higher quality) bb's say 0.3 marushin super grand master or bbbastards etc.
So: 400fps still seems a decent choice for upgrading. But as always the main thing is not just the FPS but a whole host of other factors.