jwp,
Bryan has used various chronographs. In one of his books from a few years ago, he was using an Oehler 35P with (if I recall correctly) as 12-foot screen spacing.
One of the reasons many professionals (including me) used Oehler 35's over the years was the double-check of the velocity: You get two readings for every shot, which provides a better idea of the validity of the reading. But Bryan has a youtube video out now, showing how he uses two Labradars, for similar confirmation.
