No kidding, I've been trying to talk guys out of that for years (seeing as how I was a busy gun tech for about 4 years). Always was asked "What spring do I get to give me 400fps? I want more range."
For about 4 years I ran my M24 at around 500fps (w/.20g), never really hurt anyone (cuz I am smart), but since I downgraded I find my consistancy is much better and the range is still about the same. BBs with hop up tend to stay more stable at lower velocities since they don't spin as fast as higher velocity gives.