Two arrows leave their bows at the same speed. One arrow weighs 600 grains and the other weighs 300 grains. One arrow has 5" feathers and the other arrow has 2" vanes. One arrow wobbles and the other flies straight. Which will go further? I dunno, but I can guarantee you they won't hit in the same place, by a substantial margin. Why? Wind resistance. The arrow with more inertia (weight), the arrow with a lower profile (vanes), and the arrow that doesn't wobble will have less wind resistance and therefore a greater cast, even though leaving the bow at the same speed.