I have somehow never managed to shoot my chrono...... Yet but now I am sure I have jinxed myself.
I did try out the Magneto speed type chrono this weekend and it is OK but it still takes a few minutes to get it adjusted properly but in theory you should not be able to shoot it if adjusted properly.
I checked it while shooting thru an Oehler and they were showing almost same results several times within 1 fps.