The BB's fps doesn't necessarily determine it's overall range, some guns shoot less hard and get more range, and since they lose their energy more slowly than some fast fps guns, you may be more likely to feel a hit from a long range gun. But that has to do with internal parts.
The mechanics are really complicated to me, but I find theres an optimal velocity at which bb's perform better. So although a .28 may have less fps and less kinetic energy than a .25, it's still harder for outside forces to knock it off its flight path and so it's more accurate and more likely to travel further. Whereas if you fire a .43 at 275fps (about 400fps on .2s), you can't put enough backspin velocity on it to keep it in the air for very long at that low speed.
Hope that makes sense lol