Never heard that before. I know they suggest a minimum KE in order to use some effectively.

I have used the Nail Drivers at a bit over 200 fps and they worked.

They open when they impact the skin of the animal, I don't see where speed would have any effect on how they worked. Other than a slow set up with a light arrow may not enough umph to get enough penitration.

However a 230 fps bow with an arrow over 500 grns would most likely send one right through the average deer.

My opinion anyway.

Paul