In the UK we do use crono's to measure the velocity of pellets, the bfta have set a limit just below the legal limit, legal limit minus 5 feet per second and there is a list of pellet weights and maximum velocities. Each gun is tested during a GP by a marshall and the velocity is recorded on the card.
You should be able to find the regulations on the BFTA website.
EV2 mk2 with 2009 big Nikko
HW97K with 6-24 Nikko Nighteater