You can spend into the thousands of dollars for one or spend $100 for a ProChrono and just deduct 35fps from your readings. I've had some of the "better" ones - Pact, CED - and their photocells are much more sensitive to light. Many times, depending upon the sun's angle, they just wouldn't work or gave obviously incorrect readings.
AveragEd Why do you have to deduct 35FPS when you use a ProChrono? I set it in the shade at the north end of the house. Out of five shells the differance is only 2-3FPS. When I check shells I hand weigh each shell before I put them on the reloader. Henry
Henry, that's because "hobby" chronographs like the ProChrono and others in that price range are built for handgun, rifle and archery use where there is one projectile. Shotgun-specific chronographs clock the mass of the pellets while ones like the ProChrono clock the leading pellet, which yields artificially high readings. Shotgun-specific ones are very costly; it's a lot less expensive to just do a little math.