ok heres what i think is happening, based on not being there at the time of the experiment
and of course my german not being that fluent
so with the arrow builds, did he use the same weight points for both arrows- must have, i assume.
so one set of arrows wre physically lighter in mass due to differences in shaft weight.
even though its negligible, but the lighter mass arrows will have had a higher FOC.- due to the steering arm of the arrow being lighter in weight, so improving the foc.
Now FOC works , for its intended purpose, we all know that, however it does have its shortcomings.
as the velocity starts to bleed off the projectile, the higher foc arrow starts to adopt a downwards attitude- simple aerodynamics, being that the balance point is further forward,
this forces the arrow to adopt a different ( downward angle ) flight path bringing it to earth sooner, not because there was a greater loss in velocity, but rather a change in flight attitude- due, inadvertently to the higher FOC.
flight arrows, where distance is critical, will perform better with lower FOC's, the closer to a zero FOC will allow the arrow to come back to earth still kinda parallel to the ground, where as the higher foc will come back to earth sooner in a more downwards attitude.
now for flight archery, this also comes at a bit of a compromise, lower FOC take longer to stabilize and that equates to a loss of efficiency, which robs distance.
but i think its an easy trade off, the extra distance gained due to a flatter flight attitude outweighs the minimal efficiency lost, assuming of course all the test arrows are well tuned.
so in closing, shoot two arrows the same weight out of the same bow, same velocity!
but one with a higher foc than the other, the higher foc will cover less distance.
But to be honest , we all know how this works in theory, i just would not have belived it was so evident, over such a short distance, with such an unintentional and negligible difference in FOC %.
If i am correct, this just goes to prove just how important it is to well tune , and well match your arrows.
this is a great topic, anybody else have any thoughts and ideas?