I know it is a bit aside but I have always gone through the BFTA Chrono within 10fps of what the clubs Skan, my PM-100 and my CB625. I run at 770fps +/- 5fps on my CB625. I have had 760fps the lowest (Tondu) and 778fps at North Oxon. I believed that the chrono at Tondu was running slower as Jemma's rifle came in low (put a bit of doubt in her mind I believe) but back at home was as set by Ben Taylor at 780fps.
Checked the clubs and mine by lining them all up carefully and using the Skan as our reference in the middle. Each shot through 10 times to get the reading of each one also used weighed pellets of 8.4gr to remove the weight error as much as possible.
CB625 was 2fps slower (before the Skan)
PM-100 was also 2fps slower (after the Skan)
We were therefore happy until someone managed to miss the tube and hit a LED on the Skan. Due to be posted off for repair soon.