Night Shooting (Pics)

Just a guess, I would say that you may have been shooting into the wind, It doesn't take much of a breeze to redirect flame, as for the hot particles, they may be burning powder, wouldn't be so easily redirected, but the more it burned the more it rose up.

Like I said, just a guess.

Cool pics; How many did you have to take to get the four above?

Hey-good plan! I honestly wouldn't have come up with that. Now we all know how to take cool muzzle flash pics.

If you have a DSLR and a shoe mounted flash with a manual capability, do this:
Somewhere in the menus, you'll find a "second curtain" selection for the flash sync. Selecting that will cause the flash to fire at the END of the exposure. Use the camera in "Manual", and stay with the long exposure, to give you time and make the timing easy. You'll have to manually set up the flash as well, for the ISO speed and distance, but it's pretty easy if you just set it up slowly, and think it through.
Doing this will capture the muzzle flash, and include the shooter and gun in the image. The flash won't "drown out" the muzzle flash, as long as there are no objects in the near background.