ORIGINAL: Rack-attack
If a 350 grn arrow and a 600 grn arrow travel at the same speed all the way to the target they will drop the same exact amount.
The ONLY thing that changes tragectory - bullet or arrow is the time it takes to get to the target.
I think we all recongize this, which is why we are talking about speed. Time to target is a function of speed, which is what we are talking about. An arrow (or anything else for that matter) begins to loose speed immediately after leaving the string, of course, but a heavier arrow loses speed more slowly.