Willie, the heavier arrow will travel further at the same speed. I think they have a better ration of mass to drag. Josef is about the most successful flight shooter at the moment and he is using mostly 28" or longer arrows. I don't know the weight but I imagine around 300 to 400 grains depending on the spine he needs.
The reason for this better ratio of mass to drag is that mass increases cubically with arrow diameter, whereas drag (surface area!) only increases quadratically (power 2).
For example take two douglas arrow shafts (sg 0.5 g/cm
3), 0.8 cm and 1.2 cm thick, both 26" long, which translates roughly into 220 grains and 500 grains of mass. The surface and hence drag of the heavy arrow is only 1.5 times that of the lighter one, but its mass has increased by a factor 2.25.
So although the heavy arrow has 1.5 times more drag, it has 2.25 times more kinetic energy (E=MV
2) at the same initial arrow velocity. Relative to the light arrow, It has more kinetic energy to compensate for drag (its drag coefficient will hence be lower), hence it will fly further.
We know there is a trade-off between arrow speed and arrow mass. However, because of the virtual mass of a bow, arrow speed doesn't decrease linearly with arrow mass. Taken the non-linear relation between drag and arrow mass, there is a sweet spot (arrow mass) at which a bow can shoot farthest. At that sweet spot, both heavier and lighter arrows will reduce distance.
Part of the flight shooting game (next to arrow tuning, arrow shape, drag reduction, release, ...) is to find that sweet spot of perfect arrow mass for that particular bow.
This means it is possible that an heavier arrow shot at 190 fps may fly further than a lighter arrow shot at 200 fps. I think Steve can testify to this.
