Shooting Gun Muzzle Blast Question

Took my D7000 to a shooting range recently. I would have been happy to get a few shots with the shell casing being ejected (and I did get some pics of this), but after the fact, I noticed I had actually captured the muzzle blast in one of the pics. That day, I simply set the camera to its max frame rate, i.e., 6 fps for D7000, and tried to anticipate when the shooter would fire. This pic I got unexpectedly and purely by luck. But, if I was to try and duplicate such a pic intentionally, how would you do it? How would you plan to get such a shot showing the muzzle blast? Any tips?