Actually, I do have first hand experience. My spotter's SR-25 was acting up, and we had about 2 days until game day. His rifle shoots at about 460 fps. We stuck the TK barrel in it, with a firefly bucking, and now have a beautiful flight path out to about 230-250 feet. I would take a video, but he just left for Calgarie, so I won't see him ever again to take a video.
Anyway, it does work at higher fps, but you have to have a big cylinder, because the volume of air will make it so that the cushion of air is still there. That is why it worked with the SR-25, it has a PSG-1 cylinder, so the cylinder volume is big enough that it works.