Actually it will vary depending on speed and drag. Weight will have no direct bearing on it.

The following will give you an average drop between 20 and 40 yards

Spread of arrow drop between 20 and 40 yard group

Speed (fps) Drop in inches
220 28.7
240 24.2
260 20.6
280 17.7
300 15.5
320 13.6

As you can see there is only 5" difference between 260 fps and 300 fps. It less than half that from 20 to 30 yards. Hardly something to worry about. Much greater deviations can be obtained by shooting a too light arrow that has too low an FOC or too lightly spined. The quest for speed can indeed come at great cost and little benefit.